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Hate  ^allege  of  JVgricultutc 
At  (Sfornell  UniaerHitH 


Cornell  University  Library 
TN  775.R55  1896 

Aluminium;  its  history,  occ"''* "SiPmSP^ 

3  1924  003  633  751 

Cornell  University 

The  original  of  tiiis  book  is  in 
tine  Cornell  University  Library. 

There  are  no  known  copyright  restrictions  in 
the  United  States  on  the  use  of  the  text. 







JOSEPH  W.  RICHARDS,  A.  C,  Ph.D., 





f  .     . 



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No.  810  Walnut  Stbebt. 


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Ten  years  ago  aluminium  was  an  almost  unknown  metal; 
then  it  sold  for  twelve  dollars  a  pound,  now  it  is  bought  for  fifty- 
cents  ;  then  the  yearly  production  was  less  than  is  the  present 
daily  output ;  then  only  three  books  had  been  written  about  it, 
since  then  seven  have  appeared  and  two  journals  have  been  es- 
tabHshed  to  represent  it.  The  lowering  of  the  price,  the  increased 
production,  the  wide  circulation  of  reliable  information  about 
aluminium,  have  brought  to  pass  the  dream  of  Deville,  for  it  has 
truly  become  a  metal  of  every-day  life. 

The  abundance  of  aluminium  in  nature,  the  purity  of  its  ores, 
its  wonderful  lightness  and  adaptability  to  numerous  purposes, 
indicate  that  the  goal  of  the  aluminium  industry  will  be  reached 
only  when  this  metal  ranks  next  to  iron  in  its  usefulness  to  man- 

To  assist  this  consummation  by  furnishing  all  the  reliable  in- 
formation about  aluminium,  to  thus  enlighten  the  general  reader, 
help  the  workman,  instruct  the  student,  assist  the  experimenter, 
and  in  every  way  to  speed  the  industry  on  its  destined  path, 
is  the  raison  d'etre  of  this  work. 

The  writer  thanks  the  public  for  its  generous  appreciation  of 
his  past  endeavors.  The  volume  has  been  revised  to  date,  sev- 
eral chapters  have  been  largely  re-written,  and  every  effort  has 
been  made  to  make  the  work  worthy  of  the  splendid  industry 

which  it  represents. 

Joseph  William  Richards. 

The  LEfflGH  University, 
Bethlehem,  Pa.,  October  zj,  iSgs- 



If  it  was  true  that  no  apology  was  necessary  in  presenting  a 
work  on  Aluminium  in  English,  as  stated  in  the  preface  to  the 
first  edition  of  this  book,  it  is  equally  true  that  still  less  apology 
is  necessary  in  offering  an  improvement  on  that  work. 

The  present  volume  is  designed  to  be  an  improvement  on 
the  former  one  in  the  following  respects :  Mistakes  have  been 
corrected  wherever  detected  by  the  author  or  pointed  out  by 
his  friends ;  in  some  instances  the  order  of  treatment  of  different 
parts  has  been  revised,  so  as  to  bring  them  into  strict,  logical 
sequence ;  the  more  strictly  historical  processes  are  described  in 
greater  detail,  in  order  to  preserve  a  complete  record  of  the  rise 
of  the  aluminium  industry;  chapters  have  been  added  treating 
on  the  properties  and  the  preparation  of  aluminium  compounds, 
on  the  theoretical  aspect  of  the  reduction  of  aluminium  com- 
pounds, and  on  the  analysis  of  commercial,  aluminium  and  its 
common  alloys ;  the  original  chapters  have  been  in  several  cases 
sub-divided,  and  every  part  treated  more  by  itself  and  in  greater 
detail  than  before ;  finally,  additions  have  been  made  through- 
out recording  and  describing  the  progress  achieved  in  the  last 
three  years,  with  a  completeness  which  it  is  hoped  is  up  to  the 
standard  of  the  rest  of  the  book. 

The  method  of  treatment  in  the  present  edition  will  be  found 
to  be  more  critical,  for  wherever  a  reasonable  doubt  might  be 
expressed  as  to  the  correctness  of  certain  claims,  or  a  rational 
explanation  advanced  for  certain  phenomena,  the  author  has  not 



hesitated  to  put  his  best  thought  on  the  question  and  to  state 
his  conclusions  unreservedly. 

The  friendly  criticisms  of  the  scientific  press  and  their  sug- 
gestions have  been  kept  in  view  in  preparing  this  new  edition. 
The  spelHng  "  aluminium  "  has  been  retained,  because  no  suffi- 
cient reasons  have  been  advanced  for  changing  it  to  "  alu- 
minum;" and  even  if  each  way  was  equally  old  and  as  well- 
sanctioned  by  usage  and  analogy  as  the  other,  the  author's 
choice  would  be  the  longer  spelling,  as  being  more  euphonious 
and  agreeable  to  the  ear. 

It  has  been  the  author's  endeavor  to  make  this  volume  as 
complete  as  possible,  as  accurate  as  possible,  to  write  it  in  a 
manner  which  will  be  entertaining  to  the  general  reader,  and  to 
furnish  a  treatise  which  will  be  of  practical  value  to  the  practical 
metallurgist,  as  well  as  of  scientific  merit  where  it  touches  on 
matters  of  theory. 

J.  W.  R. 

Bethlehem,  Pa.,  March  12,  i8()o. 


No  apology  is  necessary  in  presenting  a  work  on  Aluminium 
in  English.  In  1858  Tissier  Bros,  published  in  France  a  small 
book  on  the  subject.  H.  St.  Claire  Deville,  the  originator  of 
the  aluminium  industry,  published  a  treatise,  also  in  French,  in 
1859.  Deville's  book  is  still  the  standard  on  the  subject.  Until 
December,  1885,  we  have  an  intermission,  and  then  a  work  by 
Dr.  Mierzinski,  forming  one  of  Hartleben's  Chemisch-Technische 
Bibhothek,  which  is  a  fair  presentation  of  the  industry  up  to 
about  1883,  this  being  a  German  contribution.  Probably  be- 
cause the  English-speaking  people  have  taken  comparatively 
little  hand  in  this  subject,  we  find  no  systematic  treatise  on 
aluminium  in  our  language.  The  present  work  aims  to  present 
the  subject  in  its  entirety  to  the  English  reader. 

Tissier,  Deville,  Mierzinski,  and  the  German,  French,  and 
English  scientific  periodicals  have  been  freely  consulted  and 
extracted  from,  full  credit  being  given  in  each  case  to  the  author 
or  journal.  As  this  art  has  of  late  advanced  so  rapidly,  it  has 
been  a  special  aim  to  give  everything  that  has  been  printed  up 
to  the  time  of  publication. 

The  different  parts  of  the  work  are  arranged  in  what  seemed 
their  logical  order,  corresponding  closely  to  that  followed  by 
Deville.  The  Appendix  contains  an  account  of  laboratory  ex- 
periments, etc.,  several  of  which,  it  is  trusted,  may  be  of  value. 

In  conclusion,  the  author  wishes  to  thank  the  Faculty  of  his 
"  Alma  Mater,"  Lehigh  University,  for  their  permission  to  use 



his  Thesis  on  Aluminium  as  the  basis  of  this  treatise ;  also,  to 
acknowledge  his  indebtedness  to  Dr.  Wm.  H.  Greene,  of  Phil- 
adelphia, for  assistance  rendered  in  the  preparation  of  the  work 
for  the  press. 

J.  W.  R. 
Philadelphia,  November  2j,  j8S6. 


{Arranged  chronologically.^ 

Tissier .  Recherche  de  1' Aluminium.     C.  &  H.  Tis- 

sier.     Paris  :  J.  Hetzel  et  Cie.     1858. 

Uhlenhuth Die  Darstellung  des  Aluminiums.     Ed.  Uhl- 

enhuth.     Quedlinburg:  G.  Basse.     1858. 

Deville De   I'Aluminium.      H.   St.    Claire    Deville. 

Paris :  Mallet-Bachelier.     1859. 

Mierzinski .      Die  Fabrikation  des  Aluminiums.     Dr.  Stan- 

islaus Mierzinski.  Vienna :  Hartleben's 
Chemisch-technische  Bibliothek.     1885. 

Richards  (ist  Ed.) Aluminium.  Joseph  W.  Richards.  Phila- 
delphia :  Henry  Carey  Baird  &  Co.     1887. 

Richards  (2nd  Ed.) Aluminium.  Joseph  W.  Richards.  Phila- 
delphia :  Henr}'  Carey  Baird  &  Co.     i8go. 

Le  Verrier Note  sur  la   Metallurgie   de   I'Aluminium. 

U.  LeVerrier.    Paris:  BaudryetCie.  1891. 

Minet L' Aluminium.  Adolphe  Minet.  Paris  ;  Ber- 
nard Tignol.     1892. 

Lejeal L'Aluminium.     Adolphe  Lejeal.     Paris:  J. 

B.  Bailli^re  et  File.     1894. 


Fremy Enclyclop£die   Chimique.     Fremy.     Paris : 

Ch.  Dunod. 
Art :  L'Aluminium  par  Margottet  (1883). 
Art :  L'Aluminium  et  ses  Alliages  par  Wick- 
ersheimer  (1890). 

Kerl  and  Stohman Enclyclopadisches     Handbuch    der    Tech- 

nischen  Chemie.     4th   Ed.      Brunswick : 
Vieweg  und  Sohn.     1886. 
Art:  Aluminium  von  R.  Biederman. 
Watts Watts'  Dictionary  of  Chemistry. 

( xiii ) 



Ann.  de  Chim.  et  de  Phys.    .    .  Annales  de  Chimie  et  de  Physique. 

Ann.  der  Chem.  und  Pharm.    )  Liebig's   Annalen   der   Chemie    und    Phar- 

Liebig's  Ann J      made. 

Bull,  de  la  Soc.  Chim Bulletin  de  la  Soci^t^  Chimique  de  Paris. 

Chem.  News The  Chemical  News. 

Chem.  Zeit.    .    .  Chemiker  Zeitung  (Cothen). 

Compt.  Rend Comptes  Rendus  de  les  Stances  de  I'Acadd- 

mie.     Paris, 

Dingl.  Jrnl Dingler's  Polytechnisches  Journal. 

E.  and  M.  J The  Engineering  and  Mining  Journal. 

Jahresb.  der  Chem Jahresbericht    ueber    die     Fortschritte    der 


Jrnl.  Chem.  Soc Journal  of  the  Chemical  Society. 

Jrnl.  der  Pharm Journal  der  Pharmacie. 

Jrnl.  fiir  pr.  Chem Erdmann's  Journal  fiir  praktische  Chemie. 

Mon.  Scientif. Le  Moniteur  Scientifique.    Dr.  Quesnesville. 

Phil,  Mag The  London   and  Edinburgh  Philosophical 

Phil.  Trans ...  Transactions    of   the    Royal    Philosophical 


Pogg.  Ann Poggendorff's  Annalen. 

Poly.  Centr.  Blatt Polytechnisches  Central-Blatt. 

Proc.  Ac.  Nat.  Sci.  ....  Proceedings    of   the   Academy   of   Natural 

Sciences  (Philadelphia). 

Quarterly  Journal Quarterly  Journal  of  the  Society  of  Arts. 

Rpt.  Brit.  A.  A.  S Report  of  the  British  Association   for  the 

Advancement  of  Science. 

Sci.  Am.  (Suppl.) Scientific  American  (Supplement). 

Wagner's  Jahresb Wagner's     Jahresbericht     der    Chemischen 

Zeit.  fiir  anal.  Chem Zeitschrift  fiir  Analytische  Chemie. 


The  Aluminum  World  ....  New  York.  Published  monthly.  Estab- 
lished September,  1894. 

L'Aluminium Paris.      Published    monthly.       Established 

January,  1895. 



History  op  Ai<uminium. 


The  alumen  of  Pliny;  Alumen  Roccae  or  rock  alum;  Alums  and  vitriols 
confounded       ....  .......       1 

Paracelsus  distinguishes  alums  from  vitriols;  Views  of  Ettmiiller,  Stahl, 
Hoffman,  Geoffroy,  Hellot  and  Pott,  on  the  nature  of  the  base  of 
alum;  Marggraff's  dissertations  on  alum  and  its  earth;  Morveau  fixes 
the  nomenclature  of  alumina 2 

The  search  for  aluminium;  Macquer's  supposition;  Baron's  attempts  to 
reduce  alumina;  Lavoisier's  views  on  the  nature  of  alumina        .         .       3 

Ruprecht  and  Tondi's  experiments;  Criticisms  of  Savaresi,  Klaproth 
and  Karsten;  Dr.  Hare  melts  alumina  without  noticing  any  reduction; 
Sir  Humphry  Davy  attacks  the  earths  with  his  great  battery       .         .       4 

Davy's  experiments  on  reducing  alumina;  He  reduces  it  in  the  electric 
arc  in  presence  of  iron;  He  suggests  a  name  for  the  metal  ...       5 

Prof.  Benjamin  Silliman's  experiment  with  Dr.  Hare's  blow-pipe;  Oer- 
sted's attempt  to  reduce  aluminium  chloride;  Berzelius'  attempt  to 
reduce  cryolite 6 

Professor  Frederick  Wohler,  of  Gottingen,  isolates  aluminium  as  a 
metallic  powder,  in  1827 7 

Wohler  obtains  the  metal  in  globules,  in  1845;  Professor  Henri  Saint- 
Claire  Deville  obtains  aluminium  en  masse,  in  1854       .        ...        .8 

Deville's  first  attempts;  His  paper  read  before  the  French  Academy  on 
February  6,  1854 .         .       9 

The  Academy  aids  Deville  in  his  further  work  ;  A  reclamation  by 
Chenot;  Further  experiments  at  the  Ec61e  Normale;  Reduction  of 
aluminium  chloride  by  the  battery  10 

Deville's  experiments  in  manufacturing  sodium;  Installation  of  the 
sodium  process  at  Rousseau  Bros,  chemical  works  at  La  Glaci^re; 
Deville  and  Bunsen  publish  their  electrolytic  methods;  The  Emperor 
Napoleon  III.  becomes  interested  and  defrays  the  expense  of  further 
experiments H 




TheTissier  Bros,  experiment  on  producing  sodium;  Deville's  work  at 
Javel;  The  industry  on  a  firm  basis '     ^^ 

Exhibit  of  aluminium  at  the  Paris  Exposition,  1855;  Misunderstanding 
between  Deville  and  the  Tissier  Bros 13 

Tissier  Bros,   start  an  aluminium  works  near  Rouen;  History  of  this 

enterprise ^^ 

Deville  and  his  friends  put  up  a  large  plant  at  La  Glaci&re;  Removal  to 
Nanterre;  Removal  to  Pechiney  and  Co.'s  works  at  Salindres;  Tissier 
Bros,  publish  their  "Recherchessurl'Aluminium"  {1858)  .         .     15 

Deville  publishes  his  "De  I'Aluminium"  (1859);  Hi^  conclusions  as  to 
the  usefulness  of  aluminium 16 

Experiments  of  Dr.  Percy  and  H.  Rose  on  reducing  cryolite;  Manufac- 
ture of  aluminium  by  A.  Monnier,  of  Camden,  N.  J.;  Calculation  of 
cost  of  the  new  metal  by  W.  J.  Taylor 17 

The  first  aluminium  works  in  England,  at  Battersea  (1858);  Bell  Bros, 
works  near  Newcastle-on-Tyne;  Project  to  start  works  at  Berlin;  Dr. 
Clemens  Winckler's  retrospect,  1879 18 

Condition  of  the  aluminium  industry  in  1879 19 

The  industry  from  1879  to  1882;  W.  Weldon's  views  on  its  prospects  in 
1883 .     20 

The  search  for  a  substitute  for  sodium ;  Webster's  improvements  in  the 
industry .21 

H.  Y.  Castner's  invention  for  producing  sodium;  His  experiments  in 
New  York 22 

Castner's  demonstration  in  England;  Unites  with  Webster  to  form  the 
"Aluminium  Company,  Limited;  "  Large  works  at  Oldbury  near  Bir- 
mingham, stop  making  aluminium  in  1891     ......     28 

Revival  of  electric  methods,  using  dynamos  instead  of  the  battery; 
Gratzel's  process 24 

Kleiner's  process;  Hall's  process,  invented  in  1886,  essentially  different 
in  principle  from  previous  attempts 25 

Incorporation  of  the  Pittsburgh  Reduction  Co.  to  work  Hall's  process; 
Works  at  Kensington,  Pa.,  and  Niagara  Falls;  Minet's  experiments 
at  Creil  and  works  at  Saint  Michel,  Savoy 26 

The  electric-furnace  methods;  Siemens  furnace;  Grabau's  experiments; 
Mierzinski's  remarks 27 

Cowles  Bros,  process,  1885;  Plant  at  Lockport,  N.  Y.,  and  works  in 
England;  The  principle  of  the  process  .  28 

H^roult's  processes;  Principle  of  his  alloy  process 29 

The  "Aluminium  Industrie  Actien  Gesellschaft "  formed  to  work 
HSroult's  processes;  Dr.  Kiliani,  manager  of  their  works  at  the  Falls 
of  the  Rhine;  The  Hiroult  process  in  France 30 

Experiments  with  H^roult's  process  in  the  United  States;  The  "Alliance 
Aluminium  Co.,  of  London,"  formed  to  work  Netto's  sodium  process.     31 

Failure  of  the  Alliance  Aluminium  Co.;  Grabau's  improvements  in  pro- 

CONTENTS.  xvii 


ducing  sodium  and  aluminium  fluoride;  Colonel  Frishmuth's  works 
in  Philadelphia 32 

Exhibit  of  aluminium  at  the  Paris  Exposition,  1889;  Progress  of  the  in- 
dustry since  1890 33 

The  Cowles  Electric  Smelting  Co.  sued  for  infringement  of  the  Hall 
process;  Exhibits  of  aluminium  at  the  Columbian  Exposition  in  Chi- 
cago, 1893;  The  production  of  aluminium  one  of  the  great  achieve- 
ments of  the  century 34 

Statistics;  The  decline  in  the  price  of  aluminium  and  aluminium  bronze.     35 

Production  of  aluminium  in  France  from  1854  to  1892;  Production  in 
England;  In  Switzerland 36 

Production  of  the  United  States  from  1883  to  1894;  Total  aluminium 
produced  in  the  world  to  the  end  of  1892;  World's  production  in  1893; 
An  estimate  of  the  production  in  1894 37 

The  probable  production  in  1895 38 


Occurrence  of  Aluminium  in  Nature. 

Clarke's  estimate  of  the  proportion  of  aluminium  in  the  earth's  crust; 
Not  found  metallic;  Most  frequent  combinations  in  rocks,  soils  and 
clays;  Occurrence  in  some  plants;  Ricciardi's  experiments  on  the 
assimilation  of  alumina  by  plants 39 

Composition  of  the  most  frequent  aluminium  minerals;  Bauxite  the 
most  useful  mineral  for  the  aluminium  industry 40 

Localities  in  which  bauxite  occurs ;  Deposits  worked  in  the  United 
States;  Value  per  ton 41 

Analyses  of  foreign  bauxites 42 

Analyses  of  American  bauxites  43 

Laur's  generalizations  concerning  French  bauxites  .         .         .         .44 

Hunt's  generalizations  on  American  bauxites;  The  occurrence  of  cryo- 
lite in  Greenland 45 

Composition  of  cryolite;  Amount  imported  into  the  United  States;  De- 
scription of  a  small  deposit  in  Colorado 46 

Analysis  of  the  Colorado  cryolite;  The  sources  of  corundum  .         .     47 

Mining  of  corundum  in  the  United  States;  The  composition  and  proper- 
ties of  kaolin 48 

Localities  of  the  large  kaolin  beds;  Value  of  kaolin  as  an  aluminium 
ore;  Common  clays 49 

Native  sulphate  of  alumina;  Deposits  in  New  Mexico,  Colorado  and 
Ohio 50 

Economic  value  of  the  aluminium  sulphate  deposits        .        .        .        .51 

xvni  CONTENTS. 


Physicai,  Properties  of  Ai,uminium. 


Commercial  aluminium  not  chemically  pure;  The  most  frequent  im- 
purities      52 

The  influence  of  small  amounts  of  impurities  on  the  physical  properties 

of  the  metal 53 

Analyses  of  commercial  aluminium ;  Notes  on  the  analyses     .         .         .54 

Recent  analyses  of  present  commercial  metal 55 

Difference  in  the  composition  of  metal  made  by  the  sodium  and  the 
electrolytic  methods;  The  different  conditions  in  which  silicon  exists 
in  aluminium;  Rammelsberg's  analyses  ......     56 

Absorption  of  gases  by  molten  aluminium;  Dumas'  analyses;  Author's 
observations;  Tie  Verrier's  detection  of  carbon  in  commercial  alumin- 
ium  . .....     57 

Influence  of  carbon  on  the  physical  properties  of  aluminium;  Le  Ver- 
rier  detects  nitrogen  in  commercial  aluminium     ...  .58 

Influence  of  nitrogen  on  the  physical  properties  of  aluminium;  The 
color  of  pure  and  impure  aluminium      .......     59 

Tarnishing  of  aluminium  in  the  air;  Fracture  of  purest  aluminium         .     60 
Fracture  of  impure  ahiminium;   Hardness;   Testing  quality  -with  the 

knife;  Hardening  by  cold  working .61 

Comparison  of  the  hardness  of  aluminium  with  other  metals;  Specific 

gravity  .  62 

Influence  of  impurities  on  the  specific  gravity;    Increase  of  specific 
gravity  by  working  .         .  .......     63 

Comparison  of  the  specific  gravity  of  aluminium  and  other  metals        .     64 
Comparative  value  of  equal  weights  and  equal  volumes  of  the  different 

metals;  Fusibility 65 

Melting  point  determined  by  the  electric  pyrometer;  Influence  of  im- 
purities on  the  melting  point;  Volatilization;  Odor       ....     66 

Taste;  Magnetism;  Sonorousness 67 

Sound  produced  by  an  aluminium  bell,  bar  and  tuning-fork;  Alumin- 
ium sounding  boards 68 

Velocity  of  sound  in  aluminium;  Crystalline  form;  Elasticity         .         .     69 
Tensile  and  compressive  strength       ........     70 

Table  of  tensile  tests .         .     71 

Table  of  compressive  tests;  Transverse  tests  .         .  .         .     72 

General  conclusions  of  Messrs.  Hunt,  Langley  and  Hall;  Variation  of 

tensile  strength  with  the  temperature 73 

Influence  of  working  and  annealing  on   the   mechanical   properties; 

Tensile  strength  in  comparison  with  weight 74 

Comparison  of  the  tensile  strength  with  that  of  other  metals,  section 
for  section  and  weight  for  weight;  Malleability     .  ...     75 



Thickness  of  aluminium  leaf;  Color  by  transmitted  light;  Ductility      .     76 

Expansion  by  heat;  Specific  heat 77 

Determinations  of  the  specific  heat  by  Regnault,  Kopp,  Mallet,  Tom- 
linson,  Naccari,  Le  Verrier 78 

Specific  heat  and  latent  heat  of  fusion  as  determined  by  Pionchon  and 
the  author 79 

The  amount  of  heat  in  molten  aluminium;  Agreement  with  Dulong 
and  Petit's  law 80 

Slow  melting  of  aluminium  due  to  its  great  latent  heat  of  fusion;  Com- 
parison with  other  metals;  Electric  conductivity  .....     81 

Professor  Dewar's  determinations  of  the  electric  conductivity  at  very 
low  temperatures;  Conductivity  for  heat        ......     82 


Chemical  Properties  of  Aluminium. 

Atomic  weight;  Action  of  air     .         .         .         .         ,         .         .         .         .83 
Resistance    to  air  when  melted;    Action  of  air   and  water  together; 

Piqures 84 

Combustion  of  aluminium  powder  or  leaf ;  Action  of  water    .         .         .85 
Decomposition  of  water  by  aluminium  leaf;  Action  of  hydrogen  sul- 
phide and  sulphur 86 

Experiment  of  the  author  with  hydrogen  sulphide  and  molten  alu- 
minium    . 87 

Action  of  sulphuric  acid;  Ditte's  explanations 88 

Le  Roy's  quantitative  tests  with  sulphuric  acid 89 

Action  of  nitric  acid;  Ditte's  observations 90 

Experiments  of  Le  Roy,  Lunge  and  the  author  on  the  action  of  nitric 
acid;  Use  of  aluminium  in  the  Grove  battery;  Action  of  hydrochloric 

acid    ...  .91 

Action  of  hydrobromic,  hydriodic  and  hydrofluoric  acids;  Experiment 

by  the  author;  Action  of  organic  acids,  vinegar,  etc 92 

Action  of  the  acids  found  in  food;  Deville's  prediction  of  the  usefulness 
of  aluminium  for  culinary  utensils;  Lubbert  and  Roscher's  experi- 
ments with  thin  foil 93 

Balland's  exhaustive  tests  with   foods ;    Rupp's  results;    Lunge  and 

Schmid's  experiments 94 

Details  of  Lunge  and  Schmid's  tests 95 

Conclusions  from  these  tests;  Confirmation  of  these  results  by  actual 

experience  of  two  years  with  aluminium  culinary  utensils   .         .         -96 
Action  of  common  salt,  molten  and  in  solution;  Sea- water;  Aluminium 
boats ■ ^'^ 



Action  of  organic  secretions,  the  saliva,  etc 98 

Action  of  caustic  potash,  caustic  soda;  Quantitative  tests  .         .         .99 

Action  of  ammonia;  Lime  water;  Solutions  of  metallic  salts  .         .         .  100 
Action  of  solutions  of  mercury,  copper,  silver,  lead  ....  101 

Action  of  solutions  of  zinc,  alkaline  chlorides,  aluminium  salts;  Action 

of  melted  fluorspar;  Use  as  a  flux 102 

Use  of  cryolite  as  a  flux;  Action  of  molten  silicates  and  borates      .         .  103 
Action  of  fused  nitre;  Purification  of  impure  aluminium  by  nitre;  Re- 
action with  alkaline  sulphates  and  carbonates 104 

Reaction  of  aluminium  on  oxides  of  manganese,  zinc,  iron,  lead,  copper, 

barium 105 

Greene  and  Wahl's  process  of  producing  pure  manganese;  Action  of 
phosphate  of  lime,  silver  chloride,  mercurous  chloride,  carbonic  oxide, 
hydrogen,  chlorine,  bromine,  iodine,  fluorine 106 


Properties  and  Preparation  of  Aluminium  Compounds. 

General  considerations;  Position  of  aluminium  in  the  periodic  classifi- 
cation of  the  elements .  107 

Observations  on  the  structure  of  aluminium  compounds  .         .         .  108 

The  tri-valency  of  aluminium ;  Aluminates        ......  109 

Neutral  salts  of  aluminium;  Basic  salts;  General  methods  of  formation 

of  aluminium  salts  ... 110 

General  properties  of  aluminium  salts;  Chemical  reactions  in  solution; 

Reactions  before  the  blowpipe Ill 

Alumiuium  oxide;  Physical  and  chemical  properties  .  .  .  .112 
Hydrous  aluminium  oxides,  natural  and  artificial;  The  soluble  hydrate.  113 
Aluminates;  Potassium  aluminate;  Sodium  aluminates;  Barium  alumi- 

nate ......  114 

Aluminates  of  calcium,  zinc,  copper,  magnesium,  iron,  beryllium;  Alu- 
minium chloride 115 

Hydrous  aluminium  chloride;  aluminium-sodium  chloride  .  .  .116 
Double  chlorides  of  aluminium  with  phosphorus,  sulphur,  selenium, 

ammonium  117 

Aluminium-chlor-sulphydride  ;    Aluminium-chlor-phosphydride  ;    Alu- 
minium bromide;  Aluminium  iodide 118 

Aluminium  fluoride;  Methods  of  production 119 

Fluorhydrate  of  aluminium;    Aluminium-hydrogen  fluoride;    Alumin- 
ium-sodium fluoride .120 

Aluminium  sulphide;  Double  sulphides  with  sodium  and  potassium       .  121 
Use  of  aluminium  sulphide  in  the  laboratory  for  generating  hydrogen 
sulphide;  Aluminium  selenide;  Aluminium  borides      .        .        .        .122 



Aluminium  boro-carbides;  Aluminium  carbide 123 

Production  of  aluminium  carbide  in  the  electric  furnace  by  Le  Verrier  .  124 
Composition  and  properties  of  aluminium  carbide;  Aluminium  nitride  125 

Aluminium  sulphates,  anhydrous  and  hydrous 126 

Basic  aluminium  sulphates 127 

Alums;  Potash  alum;  Ammonia  alum        ....  .         .  128 

Soda  alum;  Bouble  sulphates  of  aluminium  and  the  metals;  Aluminium 

selenites 129 

Aluminium  nitrate;  Aluminium  antimonate;  Aluminium  phosphates     .  130 

Aluminium  carbonate;  Aluminium  borate 131 

Hydrous  aluminium  borates;  Aluminium  silicates;  Blast  furnace  slags  132 


Preparation  of  Aluminium  Compounds  for  Reduction. 

The  preparation  of  alumina;  Preparation  from  alums  or  aluminium  sul- 
phate        ....  .133 

Preparation  of  alumina  from  ammonia  alum     ......  134 

Method  used  by  Deville  at  Javel;  Tilghman's  method      .         .         .  135 

Webster's  process  of  making  alumina  from  potash  alum  .  .  136 

Preparation  of  alumina  from  bauxite ;  Method  uSed  at  Salindres     .         .  137 
Heating  with  soda  and  washing  out  the  aluminate  ...  .  138 

Apparatus  used  for  washing;  Precipitation  of  alumina  by  carbonic  acid 

gas 139 

Apparatus  used  for  the  precipitation ;  The  barattes  .  .         .  140 

Washing  and  drying  the  precipitated  alumina;   Behnke's  method  of 

treating  bauxite;  Lieberfs  method  141 

Muller's  method  for  extracting  alumina  from  silicates;  Use  of  common 

salt  to  decompose  bauxite;  Wagner's  method  of  treating  bauxite        .  142 
Laur's  method  of  using  sodium  sulphate  to  decompose  bauxite;  Lowig's 
experiments  on  precipitating  alumina  from  sodium  aluminate  solu- 
tion; Dr.  Bayer's  improvements      .  143 

Preparation  of  alumina  from  cryolite;  The  dry  way  ....  144 

Furnace  for  heating  cryolite  with  chalk;  Thomson's  method  .         .  145 

Conduct  of  the  operation ;  Washing  the  fusion  ....  146 

Production  of  the  carbonic  acid  gas  for  precipitation        ....  147 
Composition  of  the  precipitate;  Action  of  steam  on  molten  cryolite; 

Utilization  of  aluminous  fluoride  slags 148 

Utilization  of  the  residual  slags  from  sodium  retorts  by  fusing  with  the 

aluminous  slags;  Decomposition  of  cryolite  in  the  wet  way  .        .  149 

Method  used  by  Deville  at  Javel;  Modification  of  this  process  by  Sauer- 
wein  .............  150 

Reactions  in  Sauerwein's  process;    Weber's  method  of  decomposing 
cryolite;  Schuch's  reaction 151 

xxii  CONTENTS. 

Preparation  of  aluminium  chloride  and  aluminium-sodium  chloride       .  152 
Method  used  by  Beville  on  a  small  scale  at  Javel      .  .  .  1 53 

Manufacture  by  Deville  on  a  large  scale 154 

Furnace  used  and  working  of  the  operation       .         .  .  155 

Output  of  the  furnace;  Purification  of  the  crude  chloride         .         .         .156 
Deville's  idea  of  making  the  double  chloride;  Margottet's  description 
of  the  apparatus  used  at  Salindres  .  ...  157 

Conduct  of  the  operation  at  Salindres         .         .  .  .         .  158 

Cost  of  making  the  double  chloride  at  Salindres       .  .         .  159 

Plant  of  the  Aluminium  Company,  Limited,  at  Oldbury,  near  Birming- 
ham, England  .         .  .  .        _.  .         .   160 

Arrangements  of  the  furnaces  and  conduct  of  the  operation    .         .         .161 
Output  of  this  plant;  Purity  of  the  double  chloride  .         .162 

Castner's  method  of  purifying  the  double  chloride   .  ...   163 

Cost  of  the  purified  double  chloride;  Gadsden's  method  of  producing 

aluminium  chloride;  Count  R.  de  Montgelas'  improvement         .         .  164 
Prof.  Mabery's  process  for  producing  aluminium  chloride  in  the  electric 
furnace;  Curie's  method;    Warren's  general   process   for   anhydrous 
metallic  chlorides  .         .  ...  165 

Camille  A.  Paure's  process;  Description  by  Berthelot  .  166 

Details  of  Faure's  process;  Output  claimed;  DuUo's  method  of  making 
aluminium  chloride  from  clay  ...  ...  167 

Remarks  on  Dullo's  suggestions;  The  preparation  of  aluminium  fluoride 
and  artificial  cryolite  .  .......  168 

Berzelius'  method  of  making  artificial  cryolite;  Deville's  methods        .  169 
Pieper's  reactions  in  the  wet  way;  Bruner,  Deville  and  Hautefeuille  on 
making  aluminium  fluoride  .  .  .         .  170 

Grabau's  processes;  Aluminium  fluoride  from  aluminium  sulphate  and 
fluorspar  .  .  ...  ...   171 

Aluminium  fluoride  indirectly  and  directly  from  kaolin  .         .         .  172 

Precautions  necessary  to  obtain  it  free  from  iron 173 

The  preparation  of  aluminium  sulphide;  Fremy's  researches  .         .         .  174 
Purity  of  the  aluminium  sulphide  produced      ....  .  175 

Reichel's  results;  Experiments  of  the  author   .  ....  176 

Propositions  of  Comenge,  Petitjean,  etc.    .  .  •  177 

Lauterborn's  patent  anticipated  .  ....  178 


The  Manufacture  of  Sodium. 

Relations  of  the  production  of  sodium  to  the  aluminium  industry;  Isola- 
tion of  sodium  by  Davy,  Gay  Lussac  and  Thenard,  Curaudau      .         .  179 

Briinner's  apparatus;  Donny  and  Mareska's  condenser;  Deville's  im- 
provements at  Javel  (1855)       .  ]80 





CONTENTS.  xxiii 


The  chemical  and  physical  properties  of  sodium       .  ...  181 

Method  of  reduction  used  at  Javel;  Composition  of  the  mixtures  for  re- 
duction     ....  ....  ...  182 

Utility  of  the  different  ingredients  of  the  mixtures;  Difficulties  of  con 

densing  sodium  vapor  .         . 

Mixture  used  at  La  Glacifere  and  Nanterre;  Charging  the  apparatus 
Description    of    retorts     and    condensers ;     Manufacture    in    mercury 
bottles  ...  .        . 

The  furnace  used  for  manufacture  in  mercury  bottles 

Detailed  description  of  condensers 

Conduct  of  the  operation     .        .  ... 

Handling  of  the  condensed  sodium;  The  temperature  necessary  for  re 
ductiou  ...  .... 

Use  of  decarburized,  cast-iron  bottles;  The  continuous  manufacture  in 

Furnace  for  manufacture  in  cylinders 

Arrangement  of  the  cylinders  in  the  furnace 192 

Charging  and  discharging  the  cylinders     .  ....  193 

Tissier  Bros. '  method  of  procedure  at  Rouen 194 

Furnace  used  by  Tissier  Bros ...  195 

Charging  and  discharging  Tissier's  furnace 196 

Causes  of  loss  of  sodium;  Deville's  improvements  at  La  GlaciSre  (1857)  197 
Deville's  large  cylinder  furnace;  Difficulties  in  its  operation  .  .  198 

Deville's  attempts  to  use  cast-iron  retorts;  Deville's  improvements  at 
Nanterre  (1859)         ...  .         .  ...  199 

Necessity  of  protecting  the  iron  cylinders;  Deville  returns  to  smaller 

apparatus  ...  . 200 

Cost  of  sodium  at  Salindres  in  1872;  An  experiment  of  Deville's  in  1864; 
Wagner's  method  of  preserving  sodium  ....  .  201 

Reduction  of  potassium  and  sodium  compounds  together;  Thompson 
and  White's  method         .  ...  ...  202 

Blackmore's  process  of  reducing  carbonate   of   soda;    Thowless'   ap- 
paratus; Jarvis'  device  for  using  fire-clay  apparatus;  Castner's  process  203 

History  and  principle  of  Castner's  invention 204 

Reaction  on  which  the  process  is  based;  Form  of  furnace  used  .  206 

Experimental  furnace  erected  in  England 

Conduct  of  the  operation  in  this  furnace   . 

Yield  of  the  furnace;  Composition  of  the  residues    . 

Cost  of  sodium  by  the  Castner  process 

Erection  of  large  works  to  operate  the  Castner  process 

Description  of  the  largest  furnaces    .... 

Manner  of  working  and  output  of  these  furnaces 

Preservation  of  the  sodium;  Reactions  in  the  process 

Netto's  sodium  process;  The  Alliance  Aluminium  Company 

Details  of  Netto's  apparatus 


xxiv  CONTENTS. 


Reduction  of  sodium  compounds  b3'  electricity;  Jablochaff's  apparatus; 

Roger's  method  219 

Details  of  Roger's  experiments  ...  220 

Grabau's  observations  on  the  electrolysis  of  molten  sodium  chloride  .  222 
Details  of  Grabau's  electrolytic  process;  Castner's  process  of  electrolyz- 

ing  caustic  soda        ....  223 


Thb  Reduction  of  Aluminium  Compounds  from  the  Standpoint  of 
Thermai,  Chemistry. 

The  proper  way  to  use  the  data  of  thermo-chemistry        ....  226 

Critical  temperatures  below  which  reactions  do  not  occur        .         .         .  227 
Influence  of  physical  state  in  determining  a  reaction;  The  heat  of  forma- 
tion of  some  aluminium  compounds       ......  228 

The  heat  of  formation  of  alumina  compared  with  that  of  other  oxides; 
Elements  which  reduce  alumina  easily  .....  229 

Possibilities  of  the  reduction  of  alumina    .......  230 

Reduction  of  alumina  by  carbon;  Necessary  conditions  to  be  fulfilled  .  231 
Heats  of  formation  of  chloride,  bromide  and  iodide  of  aluminium,  and 

other  metals 232 

Deductions  as  to  the  agents  capable  of  reducing  these  aluminium  salts  233 
Heat  of  formation  of  aluminium  fluoride  and  other  metallic  fluorides  .  234 
Observations  on  the  reduction  of  aluminium  fluoride;  Heat  of  formation 

of  aluminium  sulphide  and  other  metallic  sulphides     .         .         .  235 

Observations  on  the  reduction  of  aluminium  sulphide;  Electricity  as  a 

reducing  agent         ...  236 

The  voltage  necessary  to  produce  decomposition  of  metallic  fluorides, 
chlorides,  oxides  and  sulphides;  Tabular  view  of  these  data;  Observa- 
tions thereon     ...  ......  237 

Electrolysis  of  baths  containing  several  ingredients;  Illustration  from 

Hall's  process  ...  .  938 

Illustration  from  Minet's  process;  The  voltage  required  to  decompose 

alumina  at  different  temperatures .  239 

Calculation  of  the  temperature  at  which  hydrogen  can  begin  to  reduce 

alumina;  The  same  calculation  for  carbon  .  .         .  240 

Alumina  has  been  reduced  by  carbon  in  an  iron  blast  furnace;  Peculiar- 
ity of  acetylene  gas  as  a  reducing  agent  .         .  ...  241 
Thermal  aspect  of  other  reactions  used  in  the  aluminium  industry;  The 

production  of  aluminium  chloride  from  alumina  .....  242 
The  production  of  aluminium  sulphide  from  alumina;    Peculiarity  of 
carbon  bi-sulphide  from  a  thermal  standpoint       •         .         .         .         .  244 



Reduction  op  Aluminium  Compounds  by  Means  of  Potassium  or 



Classification   of   methods ;     The  reduction   of   chlorine   compounds  ; 

Oersted's  experiments  (1824) 246 

Wohler's  experiments  (1827);  Wohler  was  repeating  Oersted's  work.  247 
Wohler  isolates   aluminium   as  a  metallic  powder ;    His  experiments 

in  1845       .  248 

Globules  of  aluminium  obtained  by  Wohler  in  1845         .         .  .  249 

Impurity  of  Wohler's  metal;  Deville's  experiments  in  1854  .  250 

Deville  obtains  pure  aluminium  in  ingots  ......  251 

Deville's  methods  devised  in  his  laboratory  and  applied  at  Javel  (1855).  252 

Details  of  the  apparatus  employed;  Conduct  of  the  operation  253 

Deville's  dissatisfaction  with  this  apparatus  and  its  results  .         .  255 

Deville  reduces  aluminium  chloride  by  sodium  vapor      .  .         .  256 

Deville's  perfected  process  as  used  at  Nanterre  (1859)       ■  •         •  ^^'^ 

Details  of  Deville's  improvements  .         .  258 

Reduction  in  crucibles;  Lining  of  crucibles      ......  259 

Reduction  on  the  bed  of  a  reverberatory  furnace      .  ...  261 

Deville's  views  on  the  aluminium  industry  in  1859   .  .  263 

The  Deville  process  as  operated  at  Salindres  in  1882         .         .         .  264 

The  chemical  reactions  in  the  process        ...  .  265 

Description  of  furnace  used  and  mode  of  operation  .         .  .  266 

Cost  of  aluminium  at  Salindres;  Niewerth's  process  .         .  268 

Gadsden's  sodium  vapor  process;  Frishmuth's  claims      .         .  .  269 

H.  von  Groussillier's  improvement;  The  Deville-Castner  process  .  270 

Description  of  Castner's  works;  Conduct  of  the  operations     .         .         .  271 

Efficiency  of  the  process;  Closing  of  these  works     ...  .  273 


REDUCTION  OF  Aluminium  Compounds  by  Means  of  Potassium  or 
Sodium  {Continued). 

Methods  based  on  the  reduction  of  cryolite;  Experiments  of  H.  Rose 

(1855) ....  274 

Experiments  of  Percy  and  Dick  (1855) 

Deville's  methods  (1856-8)  .  .        . 

Tissier  Bros',  methods;  Impurity  of  the  metal 
Wohler's  improvements  on  Tissier's  method;  Gerhard's  furnace 
Thompson  and  White's  patent;  Hampe's  experiment;  Netto's  experi- 
ments at  Krupp's  works  at  Essen    ...  ....  290 





Formation  of  the  Alliance  Aluminium  Co.  to  work  Netto's  process  .  291 
Description  of  Netto's  processes  as  actually  carried  out  ....  292 
Return  from  Netto's  process;  The  apparatus  used  at  Essen      .         .  293 

Netto's  other  devices;  Failure  of  the  Alliance  Aluminium  Co. ;  Grabau's 

process  (1887) 294 

Advantages  of  Grabau's  method  of  reducing  aluminium  fluoride  .  295 

Reactions  in  Grabau's  process;  Description  of  the  operation  .  .   296 

Description  of  the  furnace  and  apparatus  used  .....  297 

Great  purity  of  the  aluminium  produced  by  Grabau         ....  299 


Reduction  of  Aluminium  Compounds  by  the  Use  of  Ei<ectricity. 

Preliminary  observations  on  the  laws  of  electrolysis        .  .         .  301 

Calculation  of  the  voltage  necessary  to  decompose  aluminium  com- 
pounds      .         .  .         .  .         .  .         .  302 

Utilization  of  such  calculations;  Electrolysis  of  aqueous  solutions  303 

Electrolysis  using  a  soluble  anode      ....  ...  304 

Electrolysis  using  insoluble  anodes    .  305 

Electrolysis  of  baths  containing  several  compounds  ....  306 
Deposition  of  aluminium  from  aqueous  solution;  Thomas  and  Tilly's 

patent        .         .  307 

Corbelli's  process;  Thompson's  claims;  Gore's  experiments    .         .         .  308 

Dr.  Gore's  error;  Jeangon's  process  309 

Successful  plating  by  the  Harvey  Filley  Plating  Co.,  of  Philadelphia; 
Bertrand's  assertion;  Braun's  methods  .......  310 

Dr.   Fischer's  experience  with  Braun's  method;    Farmer's  apparatus; 
Senet's  process ;    Frishmuth's  plating ;     Overbeck   and   Niewerth's 
patent        .         .  ...  .311 

Reinbold's  recipe;  Count  R.  de  Montgelas'  patents  .  312 

A.  Walker's  methods  of  procedure     .  ...  .         .  313 

Bull's  proposition;  Burghardt  and  Twining's  patents        ....  314 

Patents  of  Gerhard  and  Smith;  Taylor  and  Coulson;    Experience  of 

Sprague,  Dr.  Winckler  and  Dr.  Gore 3I5 

Opinions  of   Dr.   Mierzinski,  Hampe  and  Watt;  Experiments  of   Dr. 

Lisle;  Aluminium  plating  on  the  Philadelphia  Public  Buildings  .  316 

Aluminium  plating  by  Mr.  Darling  at  the  Tacony  Metal  Co. 's  works, 

Philadelphia gjy 

Non-aqueous  electric  processes;  Difficulty  of  a  satisfactory  classification.  318 
Davy's  experiments  (1810);  Duvivier's  experiment  (1854)  .  .  .319 
Bunsen's  and  Deville's  methods  (1854)      ...  .         .  320 

Details  of  Deville's  apparatus  32i 

Details  of  Bunsen's  apparatus    .         .  ....  322 


Deville  and  Caron's  method  of  plating  aluminium  on  copper  .         .  323 

Deville's  experiments  not  an  anticipation  of  Hall's  process;  Le  Chatel- 

lier's  patent      .  ...  324 

Monckton's  proposition;  Gaudin's  process;  Kagensbusch's  process        .  325 
Berthaut's  proposition  to  use  dynamos;  Gratzel's  process        .         .         .  326 
Apparatus  used  by  Gratzel;  Later  modification  of  his  process  .         .  327 

Prof.  Fischer's  criticism  of  Gratzel's  process;  Operation  of  the  process 
at  Bremen         .         .  ....  ....  328 

Abandonment  of  the  Gratzel  process;  Cowles  Bros.'  process   .         .         .  329 
Professor  Mabery's  description  of  the  Cowles  electric  furnace         .         .  330 

Dr.  T.  Sterry  Hunt's  remarks     ...  331 

Bradley  and  Crocker's  form  of  retort  used  by  the  Cowles  Co.  .         .  382 

A.  H.  Cowles'  form  of  furnace  for  continuous  working;  W.  P.  Thomp- 
son's paper  on  the  Cowles  process,  read  in  England     ....  333 
Cowles  Bros',  plant  at  Lockport,  N.  Y.;  Details  of  the  furnaces      .         .  334 

Charging  the  furnaces .  335 

Details  of  the  operation  of  Cowles'  furnaces  336 

The  enlarged  plant  at  Lockport         .  339 

The  Cowles  Syndicate  Co.'s  works  at  Stoke-on-Trent,  England       .        .  340 

Analyses  of  Cowles  Bros',  aluminium  bronze 341 

Analyses  of  ferro-aluminium  and  slags      .  342 

The  reactions  in  Cowles  Bros',  process 343 

Electrolysis  necessarily  a  secondary  factor  in  the  operation  of  these 

furnaces    ....  344 

H.  T.  Dagger's  experiment  with  the  alternating  current  in  a  Cowles' 
furnace     .......  ....  345 

History  of  the    suit — Pittsburgh   Reduction   Co.    vs.    Cowles   Electric 

Smelting  and  Aluminium  Co. 346 

Menges'  patent;  Farmer's  process;  Kleiner's  process  .         .  347 

Kleiner's     experiments    at    Schafthauseu ;      Experimental    plant    in 

England  348 

Dr.  Gore's  report  on  Kleiner's  process 349 

Output  of  aluminium  by  this  process;  Purity  of  the  metal      .         .         .  352 
Kleiner's  process  outclassed  by  later  processes;  Lossier's  proposition  to 

decompose  natural  silicates  of  aluminium 
Omholt's  furnace;  Minet's  process  . 
Apparatus  used  in  Minet's  process  . 
Composition  and  properties  of  the  baths  . 
Minet's  views  on  the  reactions  in  his  baths 
Electrical  measurements  on  Minet's  pots 
Separation  of  iron  and  silicon  by  a  carefully  regulated  current  .  .  360 
Output  and  quality  of  aluminium;  Installations  of  this  process  .  .  361 
Minet's  plant  now  working  on  the  Hall  process;  Feldman's  process  .  362 
Uselessness  of  Feldman's  methods;  Warren's  experiments  .  .  .363 
Zdziarski's  patent;  Grabau's  apparatus 364 


xxviii  CONTENTS. 


Roger's  process;  Details  of  experiments    .......  365 

Dr.  Hampe  on  the  electrolysis  of  cryolite          .         .                  ...  368 

History  of  Hall's  experiments;  Interference  with  H^roult  in  the  United 

States  patent  ofi&ce          .                  ...                  ....  373 

Specifications  and  claims  of  Hall's  patents 374 

Installation  of  Hall's  process  at  Pittsburgh 376 

Conduct  of  the  operation  in  Hall's  pots 377 

Consumption  of  carbon  anodes 378 

Alumina  used  in  the  process;  Efficiency  of  the  electrolysis  .  .  .  379 
Estimate  of  cost  of  aluminium  by  the  Hall  process  in  1889;  Enlarge- 
ment of  the  plant  in  1890 381 

Removal  and  enlargement  of  the  plant  in   1891 ;   The  Niagara  Falls 

plant 382 

Total  output  of  the  Pittsburgh  Reduction  Co.'s  works;  Efficiency  of 

the  process        .                  383 

Chemical  reactions  in  Hall's  baths;  Alumina  is  the  compound  primarily 

decomposed      ...                  ......                  .  384 

Theory  of  an  aluminium  oxy-fluoride  not  proven;  Hdroult's  processes.  386 

Similarity  of  Hferoult's  first  process  to  that  of  Hall          ....  387 

HSroult's  alloy  process;  Installation  at  the  Falls  of  the  Rhine        .         .  388 

Description  of  furnaces  used       .                  .......  389 

Conduct  of  the  operation ...  390 

Output  at  full  efficiency;  Theoretical  output              .....  392 

H^roult's  alloy  process  not  essentially  electrolytic  in  its  operation          .  393 

HSroult's  apparatus  for  pure  aluminium  ....  394 
Recent  enlargements   at  the   Rhine   Falls  ;    The   Heroult  process  in 

France 395 

Hdroult's  alloy  process  at  Boonton,  N.  J 896 

Details  of  cost  of  pure  aluminium  atNeuhausen;  Faure's  electrolytic 

process      ...                  398 

Winkler's  patent;  Willson's  crucible 399 

Grabau's  electrolytic  process;  Bucherer's  patent       .....  400 

The  Neuhausen  sulphide  process .  401 



Reduction  by  carbon  without  the  preseuce  of  other  metals;  Chapelle's 

attempt ...  402 

Reinar's  experiment  with  alum;  Thowless'  claim      .  ...  403 

Patent  of  Pearson,  Liddon  and  Pratt;  Bessemer's  ideas   ....  404 
Reduction  by  carbon  and  carbon  dioxide;  Morris's  claims       .         .         .  405 

CONTENTS.  xxix 


Ideas  of  P.  A.  Emanuel;  Reduction  by  hydrogen 406 

Gerhard's  #patent;    Success  of   H.    Warren   in   reducing  alumina  by 

hydrogen 407 

Reduction  by  carburetted  hydrogen;  Fleury's  experiments;  Petitjean's 

statement 408 

Experiments  of  L^b^deef,  Dr.  Lisle,  R.  E.  Green 409 

Reduction  by  cyanogen;  Knowles'  patent;  Corbelli's  process;  Experi- 
ments of  Deville  and  Lowthian  Bell 410 

Reduction  by  double  reaction;  Comenge's  process;  Niewerth's  furnace  411 
Process  of  G.  A.  Faure;  Reduction  by  or  in  presence  of  copper;  Calvert 

and  Johnson's  experiments      ........  413 

Evrard's  method  of  making  aluminium  bronze;  Benzon's  patent  .  414 

Faure's  patent ....  415 

Experiments  by  BoUey,  List,  Dr.  Lisle  and  Hampe  .         .         .416 

Experiments  of  Reichel  and  the  author;  Processes  of  A.  Mann  and  L.  Q. 

Brin  ...  .        .  ....  417 

Reduction  by  or  in  presence  of  iron;  Experiments  of  Comenge,  Lauter- 

born,  Reichel  and  the  author;  Niewerth's  process        ....  418 

Thompson's  method 419 

Calvert  and  Johnson's  experiments 420 

Chenot's  reclamation;  Use  of  spongy  iron         .         .  .  .  421 

Faraday  and  Stodart's  investigations;  Wootz  steel 422 

Presence  of  aluminium  in  pig-iron ;  Reports  by  various  analysts  .  .  423 
Billings'   attempt  to   reduce   alumina  in  contact  with  iron;  Cleaver's 

patent  .  .  ...  .        .  424 

Ostberg's  statement  about  aluminium  in  pig-iron;  Brin  Bros.'  process    .  425 
Baldwin's  process  for  treating  foundry  iron        .  .  .         .  426 

Alloy  of  the  Williams  Aluminium  Company;  Bamberg's  method  .  .  427 
Aluminium  in  pig-iron  from  Marshall  Bros.'  Newport  furnace  .  ,  428 
Reduction  by  or  in  presence  of  zinc;  Statements  of  Bdk^toff,   DuUo, 

Basset        .  ...  429 

Wedding's  remarks  on  Basset's  process;  Experiment  by  the  author        .  431 
Works  of  F.  J.  Seymour  at  Findlay,  Ohio  ...  .         .  432 

Lauterborn's  method  of  reduction  by  zinc  .  ....  433 

Clark's  doubtful  processes  ....  ...  434 

Dr.  Lisle  on  reducing  aluminium  sulphide  by  zinc;  Bamberg's  patent; 

Reduction  by  lead    ...  435 

Reduction  by  manganese;  Weldon's  claim;  Greene  and  Wahl's  observa- 
tions   t 436 

Reduction  by  magnesium;  Gratzel's  patent;  Roussin's  statement;  Mont- 

gelas'  patent;  Winkler's  experiments  on  alumina  .  .        .   437 

Reduction  by  antimony;  Lauterborn's  formulas;   Experiment  by  the 

author 438 

Reduction  by  tin;  Process  of  Howard  and  Hill;  Dr.  Lisle's  successful 

experiments      .  439 



Reduction  by  phosphorus;  Grabau's  process     .         .                  ...  440 
Reduction  by  silicon;  Wanner's  claims «•         -441 


Working  in  AItItminium. 

Melting;  Deville's  recommendations 442 

Biederman's  directions;  The  author's  methods  .  ...  443 

Bauxite  and  magnesite  linings  for  crucibles  and  furnaces  .         .  444 

Casting;  Deville's  remarks  445 

Casting  under  pressure        .  .....  .  446 

Aluminium  hollow- ware  casting;   Purification  of  aluminium;   Freeing 

from  slag  .         .  447 

Freeing  from  dissolved  impurities 449 

Removal  of  zinc  by  distillation;  Test  of  Buchner's  method  of  purifica- 
tion by  hydrogen  gas       .  .  450 

Purification  by  other  gaseous  reagents;  Mallet's  method   of  making 

chemically  pure  aluminium 451 

Ive  Verrier's  experiment  with  alkaline  fluoride;  Use  of  sodium  to  re- 
move dissolved  gases;  Annealing;  Hardening 452 

Effect  of  chilling;  Rolling;  Beating  into  leaf 453 

Rolling  into  tubes  by  the  Mannesmann  process;  Very  fine  tubes  made 

by  Ivins,  of  Philadelphia;  Drawing  into  wire        .  .         .  454 

Stamping  and  spinning;  Grinding,  polishing  and  burnishing  .         .  455 

Special  polishes  for  aluminium;    Engraving;    Cleaning  and  pickling; 

Mat  .         .  ...  456 

Welding  by   electricity;    Soldering;    Requirements   of   a    satisfactory 
solder;  Difficulties  peculiar  to  aluminium  .         .  .         .  457 

Deville's  views  on  soldering  aluminium     .  .         .  458 

Mourey's  first  practical  solders  .  ...  ...  459 

Bell  Bros. '  method  of  using  Mourey's  solders  .....  461 

Frishmuth's  solders;  Schlosser's  solder  for  dental  work  ....  462 

Bourbouze's  solder  of  aluminium  and  tin;  Thowless' patent  solder  .  463 

Patents  of  Sellon  and  Sauer;  Novel's  alloys  for  soldering  .  .  .  464 
Land's  mechanical  method;  Aluminium  specially  prepared  for  soldering  465 
Special  fluxes  recommended;  Roman's  solder  .         .  .  466 

The  "Alsite"  solder;  The  phosphorized  solder  of  Mr.  Joseph  Richards, 

of  Philadelphia 467 

Success  of  Richards'  phosphorized  solder;  Methods  of  using  .  .  .  468 
Coating  other  metals  with  aluminium;  Veneering  as  practiced  by  M. 

Sevrard     .         .  469 

Dr.  Winckler's  experience  .  470 

CONTENTS.  xxxi 


Dr.  Gehring's  method  of  aluminizing;  Broadwell's  process  for  coating 
sheet-iron  ......  471 

Plating  other  metals  on  aluminium;  Gilding  and  silvering  by  Mourey 

and  others 472 

Veneering  with  silver  or  platinum;    Rolling  together  aluminium  and 
copper  sheet;  Wegner  and  Guhr's  methods  for  electro-plating  and 
coloring;  Neeson's  methods;  The  uses  of  aluminium    .         .         .         .473 
The  place  of  aluminium  among  the  useful  metals    .  ...  474 

The  first  articles  made  of  aluminium;  Use  in  the  French  army  .  .  475 
Recommendations  of  the  German  military  commission;  Use  for  boats  .  476 
The  yacht  "  Vendenesse;"  The  French  aluminium  torpedo  boat  .  .  477 
Explorer  Wellman's  boats  and  sledges;  The  yacht  "Defender;"  Use  for 

vehicles  and  flying  machines 478 

Use  architecturally  and  for  decorations;  Suitability  for  mine  cages  479 

Use  in  surgery;  Dental  plates  ...  .         .  .  480 

Use  for  scientific  instruments;  Captain  Gordon's  sextant  .         .         .481 

Advantages  of  aluminium  for  engineering  and  electrical  instruments; 

Chemical  and  bullion  balances        .         .  482 

Troemner's  assay  balances;  Use  for  aluminium  for  minor  coinage  .  .  483 
Advantages  and  suitability  for  coinage;  Use  for  chemical  apparatus  .  484 
Use  for  culinary  utensils;  Its  well-established  advantages 
Use  for  table  ware;  Disadvantages  for  some  articles 
Aluminium  constructions;  Use  in  the  battery 
Substitution  for  lithographic  stone;  Strecker's  directions 
Use  for  flash-light  powder;  Recipes  of  Villon  and  Black 
Miscellaneous  uses      ........ 



Ai,i,OYS  OF  Aluminium. 

General  remarks;  Methods  of  making  the  alloys      .         .  .         .  492 

Division  of  the  alloys  into  two  classes;  Influence  of  Aluminium  on  the 

color  of  other  metals         ...  493 

Contraction  in  alloying;  Influence  of  aluminium  on  the  specific  gravity 

of  other  metals  .  494 

Alloys  with  copper  and  iron  to  be  considered  separately;  Alloys  with 

antimony 495 

Unusual  property  of  one  antimony  alloy;  Roche's  unstable  alloy  .  .  496 
Aluminium   and   arsenic;    Aluminium   and  bismuth;    Aluminium   and 

boron         .        .  497 

Aluminium  and  cadmium;  Aluminium  and  calcium         ....  498 

Aluminium  and  chromium;  Langley's  alloy 499 

Aluminium  and  cobalt;  Lejeal's  test;  Aluminium  and  gallium        .        .  500 

xxxii  CONTENTS. 


Aluminium  and  gold;  Roberts-Austin's  tests;  Niirnberg  gold;  Andrews' 

experiments      ....  ....•••  501 

Peculiar  properties  of  the  violet  alloy  discovered  by  Roberts-Austin        .  502 

Aluminium  and  lead;  Cupellatiou  of  aluminium 503 

Aluminium  in  anti-friction  and  type  metal;  Aluminium  and  magnesium.  504 

Aluminium  and  manganese;  Cowles'  alloy •  505 

Aluminium  and  mercury;  Deville's  mistake;  Simple  experiment  by  the 

author;  Cailletet's  method  of  amalgamation  .....  506 

Joule's  electrical  experiment;  Gmelin's  observation;  Method  of  amal- 
gamation by  Watts;  Bailie  and  Fury's  study  of  the  subject  .  507 
Composition  and  properties  of  a  definite  aluminium  amalgam  .  .  508 
Action  of  air,  water,  acids  and  other  metals,  on  aluminium  amalgam; 

Aluminium  and  molybdenum  ........  509 

Aluminium  and  nickel;  Tissier's  tests        .  .....  510 

I^ejeal's  alloy  with   nickel  ;    The   Pittsburgh    Reduction   Co.'s   alloy; 

Aluminium- nickel-copper  alloys 511 

Alloys  of  Sauvage,  Baudrin,  Webster;  "Neogen"  .  .  .  512 

Webster's  patented  alloys  ...  ......  513 

"  Lechesue;  "  Method  of  production  and  properties  .         .  515 

Cowles  Bros.'  "Aluminium  Silver"  and  "Hercules  Metal;"  Andrew's 

alloys;  Aluminium  and  phosphorus  ...  .         .  516 

Aluminium   and   platinum;    Aluminium   and  silicon ;    Alloys   formed 

while  melting  aluminium  in  crucibles  ......  517 

Influence  of  silicon  on  commercial  aluminium  .         .  .         .  518 

Aluminium  and  selenium;  Aluminium  and  silver      .....  519 

Silver  alloy  for  dental  plates;  "  Tiers  Argent  " 520 

Aluminium  and  sodium;  Aluminium  and  tellurium  ....  521 

Aluminium  and  tin;  Bourbouze  alloy .  522 

Decomposition  of  some  aluminium-tin  alloys 523 

Aluminium  deleterious  to  tin-foil;  Heycock  and  Neville,  and  Minet,  on 

the  fusing  points  of  aluminium-tin  alloys       ......  524 

Aluminium  and  titanium;  Wohler's  alloy         ......  525 

Levy's  alloy;  Alloy  made  by  the  Pittsburgh  Reduction  Company  .  .  526 
Le  Verrier's  tests  of  titanium  alloys;  Aluminium  and  tungsten;  Tests 

by  he  Verrier    .... .  ,527 

Aluminium   and  zinc;    How  zinc   crept   into   some   early  commercial 

aluminium        ....  .  ...  .  528 

Aluminium  hardened  by  zinc  and  copper;    Use  of  aluminium  in  the 

galvanizing  bath  and  in  Parke's  desilverizing  process  ....  529 

Aluminium-zinc-copper  alloys;  Aluminium  brasses 530 

Baur  and  Farmer's  aluminium  brasses;  Tests  of  Cowles  Bros',  brasses.  531 

Professor  Tetmayer's  tests  of  aluminium  brasses 532 

Richards'  bronze ....  533 


Ai,uminium-Coppe;r  Ai<i,oys. 


Division  into  two  classes;  General  properties 534 

Melting  points;  Indications  of  chemical  alloys 535 

Alloys  containing  small  amounts  of  copper  .  ...  536 

Aluminium   hardened   by   copper;    Tests  of  these   alloys  by   Captain 

Julien        ...  537 

Aluminium    hardened    by   German    silver;    Alloys   containing   small 
amounts  of  aluminium;  Aluminium  bronzes        ...  .  538 

History  of  the  aluminium  bronzes 539 

Constitution  of  aluminium  bronzes;  Are  they  chemical  combinations?  540 
Morin's  arguments  to  prove  that  the  bronzes  are  chemical  alloys  .  .  541 
Action  of  small  amounts  of  aluminium  on  bronze,  brass  and  copper  .  542 
The   reducing   action   of   aluminium   on   dissolved    oxides   in  molten 

metals       .  543 

Bronzes   made   from   alumina   versus  those   made  with   metallic   alu- 
minium      544 

Method  of  preparing  the  bronzes  industrially  .  ....  545 

Influence  of  impurities  in  the  aluminium  or  copper  on  the  properties 
of  the  bronzes  ......  ....  546 

Re-melting  the  bronzes  improves  their  quality  .....  547 

Fluidity  of  the  bronzes  when  melted;  Casting  the  bronzes       .         .         .  548 
Thomas  D.  West  on  "  Casting  Aluminium  Bronze  "  .  .  549 

Shrinkage  of  the  bronzes  in  cooling;  Color      .         .  £52 

Specific  gravity  of  the  bronzes;  Hardness  ....  .  553 

Transverse  and  compressive  strength        ...  .  554 

Tensile  strength;  Lechatelier's  tests  .         .  .  .         .  555 

Tests  of  tensile  strength  by  Deville,  Strange,  at  the  Watertown  Arsenal 
and  Washington  Navy  Yard    .........  556 

Details  of  tests  of  Cowles  Bros',  bronzes .  557 

Diagram  showing  comparison  of  the  strength  of  wrought-iron,  tool- 
steel,  and  two  aluminium  bronzes  ........  558 

Professor  Tetmayer's  tests  of  the  strength  of  the  bronzes        .         .         .  559 
Diagram  showing  the  variation  of  strength  and  ductility  of  the  bronzes 
with  increasing  proportions  of  aluminium;  Le  Chatelier's  test  of  the 

strength  at  various  temperatures 560 

Annealing    and    hardening    the    bronzes;    Forging,    hammering  and 

rolling -561 

Filing,  chipping  and  planing  the  bronzes 562 

Anti-friction  qualities  of  the  bronzes 563 

Conductivity  for  heat  and  electricity;  Resistance  to  corrosion         .         .  564 
Suitability  of  the  bronzes  for  marine  construction,  chemical  purposes 
and  statuary      .  566 

xxxiv  CONTENTS. 


Various  uses  to  which  the  bronzes  are  applied;  Suitability  for  heavy 

guns  .  ... 

Suitability  for  propeller  blades 
Brazing  and  soldering  the  bronzes 
Silicon-aluminium  bronze  . 
Phosphor-aluminium  bronze;  Boron-aluminium  bronze 

.  568 
.  569 
.  570 
.  571 


Aluminium-Iron  Ahoys. 

Iron  in  commercial  aluminium  .         .  ......  672 

Alloys  made  by  Tissier  Bros.,  Michel,  and  Calvert  and  Johnson  .  .  573 
Ferro-aluminium  ;    Manufacture   directly   from   alumina  or    from   the 

metals       .         .  ...  .  .         ■  574 

Aluminium  in  commercial  steel,  wrought-iron  and  pig-iron;  Effect  of 

aluminium  on  the  properties  of  steel      .......  575 

Faraday's  experiments  with  Wootz  steel 576 

Mitis  castings;  Use  of  aluminium  in  casting  soft  steel      .  .         .  577 

Experiments  of  Gilchrist  and  R.  W.  Bavenport  ....  579 

Spencer's  experiments  on  casting  steels    .  .....  580 

' '  Steel-aluminium  ' '  for  use  in  steel ;  Effect  of  aluminium  on  wrought- 
iron  .  ...  581 

History  of  the  Mitis  process  582 

Rise  and  progress  of  the  Mitis  process;  Raw  material  used      .         .         .  583 
Composition  of  a  melt  of  mitis  metal ;  Analyses  of  mitis  castings    .         .  584 
The  process  of  making  mitis  castings        .......  585 

Conduct  of  the  process  at  the  Chester  Steel  Casting  Works  .  .  .  586 
Explanation  of  the  action  of  aluminium  in  making  mitis  castings;  Ost- 

berg's  views  .....  .....  587 

R.  W.  Davenport's  explanation  inadequate        .  ....  588 

The  author's  explanation  of  the  increased  fluidity  of  the  melt         .         .  589 
Why  mitis  castings  are  without  blow-holes        .  ....  590 

Discussion  of  Davenport's  experiment  and  Howe's  explanation  .  .  592 
Professor  Le  Verrier's  explanation  ;  Professor  Arnold's  experiment  .  593 
Summary  of  the  author's  views;  Influence  of  aluminium  in  the  puddling 

furnace .         .  ...  594 

Influence  of  aluminium  on  cast-iron  .         ......  595 

Systematic  investigation  of  this  subject  by  Messrs.  Keep,  Maybery  and 

Vorce         .         .  ....  ....  596 

General  outline  of  Keep's  tests 597 

Effect  of  aluminium  on  the  solidity  of  the  castings;  Does  the  aluminium 

remain  in  the  iron  ? 59g 

Effect  of  aluminium  on  the  transverse  strength  of  castings  .  .  .  599 
Effect  on  the  elasticity  of  the  castings 600 



Effect  on  the  grain  of  the  castings 601 

General  effect  of  aluminium  on  the  fluidity  of  cast-iron;  Shrinkage        .  602 
Effect  on  the  hardness  of  the  castings        .  ...  .  603 

Practical  advantages  in  pouring  the  castings;  General  testimony  of  ex- 
perienced foundrymen     .         .  .  ....  604 

Rationale  of  the  action  of  aluminium  on  cast-iron    ...  .  605 


Analysis  of  Ai,uminium  and  Aluminium  Alloys. 

Ingredients  to  be  determined;  Qualitative  tests  to  precede  the  quantita- 
tive analysis ...  606 

Qualitative   blow-pipe  tests;  The   specific  gravity  as   an  indication  of 
purity        .  ...  ....  607 

Schulze's  test  of  the  purity  of  commercial  aluminium;  Determination 
of  silicon  .         .  .  .  ....  608 

Separation  of  combined  and  graphitic  silicon 609 

Regelsberger's  method  for  dissolving  and  estimating  silicon   .         .  610 

Determination  of  iron  and  aluminium .611 

Separations  of  iron  from  aluminium  613 

Determination  of  lead;  Determination  of  copper;  Determination  of  zinc  614 
Determination  of  tin;  Determination  of  silver;  Determination  of  sodium  615 
Determination  of  chlorine;  Detemiination  of  carbon;  Determination  of 

fluorine  .         . 616 

Determination  of  titanium;  Determination  of  chromium          .         .         .  617 
Analysis  of  ferro-aluminiums;  Difficulty  of  estimating  aluminium  prop- 
erly; Yates'  method  of  procedure 618 

Chancel's  separation  of  iron  from  aluminium;  Peter's  modification  of 

Chancel's  separation;  Thompson's  experience 619 

Satisfactory  separation  of  iron  from  aluminium  by  potassium  cyanide; 

Precipitation  of  iron  by  tri-methylamine 620 

Blair's  procedure  for  separating  iron  from  aluminium      .  .         .  621 

Electrolytic  separations  of  iron  from   aluminium;    Classen's  method; 
Professor  Smith's  method        ...  .  .         .  622 

Stead's  method  of  separating  iron  from  aluminium;  Analysis  of  alu- 
minium bronzes  ...  .....  623 

Determination  of  tin,  lead  and  copper  in  the  bronzes       ....  624 

Determination  of  iron,  aluminium,  zinc,  cobalt  and  nickel       .         .         .  625 
Analysis  of  aluminium-zinc  alloy;  Analysis  of  aluminium-tin,  alumin- 
ium-silver, aluminium-nickel,  aluminium-manganese  and  aluminium- 
lead  alloys        ...  626 

General  remarks  on  the  usefulness  of  making  qualitative  tests  prepara- 
tory to  a  quantitative  analysis  .  627 

Index  ...  ...  629 




Pliny*  tells  us  that  alumen  was  the  name  of  several  kinds  of 
salts  used  in  dyeing,  a  white  kind  for  dyeing  bright  colors  and 
a  dark  kind  for  dull  colors ;  that  all  alumen  had  an  astringent 
taste  and  was  colored  black  by  the  juice  of  the  pomegranate 
(a  reaction  caused  by  iron).  From  all  we  can  learn  in  the 
writings  of  Pliny  and  Columella,  it  appears  that  the  white 
alumen  must  have  been  a  mixture  of  aluminium  sulphate  with 
more  or  less  sulphate  of  iron.  Why  it  was  called  alumen  is 
not  certainly  known,  but  it  was  probably  derived  from  lumen, 
light,  in  allusion  to  its  brightening  the  colors  when  used  in 

About  the  eighth  century  a  very  pure  alumen  was  made  in 
Rocca,  near  Smyrna,  and  hence  called  alumen  Rocca,  or  in 
modern  times,  rock  alum.  This  was,  indeed,  a  pure  sulphate 
of  aluminium  with  sulphate  of  potash;  in  fact,  our  modern 
alum,  diflfering  from  the  ancient  alumen  in  that  it  contained 
potassium,  and  was  manufactured  with  care  instead  of  being 
merely  a  natural  substance.  The  old  name  was,  however,  still 
attached  to  the  new  product,  and  included  in  its  scope  the 
vitriols,  that  is,  the  sulphates  of  iron  and  copper.  Even  in  the 
thirteenth  century  alum  and  vitriol  vvere  named  together  as  re- 
lated substances. 

*  Book  35,  chapter  15. 



Paracelsus*  in  the  sixteenth  century  first  separated  alum  and 
vitriols,  on  the  ground  that  the  base  of  the  vitriols  was  metallic 
and  that  of  alum  earthy. 

Ettmiillerf  discovered  in  1684  that  "alum  is  obtained  by 
acting  on  clay  with  sulphuric  acid." 

Stahl  in  1702  expressed  clearly  his  conviction  that  the  un- 
known base  of  alum  was  of  the  nature  of  lime  or  chalk,  and  for 
fifty  years  thereafter  this  was  the  generally  accepted  idea. 

Hoffman  $  twenty  years  later  announced  that  the  base  of 
alum  appeared  to  him  to  be  a  true,  distinct  earth.  GeofiTroy, 
in  1728,  Hellot,  in  1739,  and  Pott,  in  his  famous  Lithogeognosia, 
in  1746,  all  reiterated  this  statement  with  increasing  certainty, 
until  it  was  finally  generally  received  as  an  accepted  fact,  and 
the  last  named  chemist  gave  it  the  name  of  thonichte  erde,  or 
terre  argilleuse. 

In  1754  Marggraff,§  in  three  able  dissertations  on  alum  and 
its  earth,  showed  that  this  earth  is  certainly  a  distinct  substance, 
that  it  exists  in  all  natural  clays  and  can  be  extracted  therefrom 
by  sulphuric  acid,  that  the  part  of  the  clay  not  touched  by  the 
acid  is  silica,  and  that,  therefore,  the  purest  white  clay  contains 
only  silica  and  the  earthy  base  of  alum.  These  memoirs  settled 
conclusively  the  composition  of  clay,  and  give  rise  to  the  term 
argil  or  argil  pier  as  the  name  of  the  earthy  base  of  alum.  It 
was  thus  called  until  1761,  when  Morveau,||  intent  on  revising 
chemical  nomenclature,  decided  that  since  alum  was  called  sel 
alumineux,  the  proper  name  for  its  base  should  be  altimine, 
thus  avoiding  all  confusion  with  argille  and  terre  argilleux,  the 
terms  designating  clay  and  clayey  earth.  In  German,  however, 
the  earth  of  alum  is  still  called  thonerde — clay  earth ;  in  English, 
the  French  alumine  was  adhered  to  until  about  1820,  when  it 
was  anglicised  into  alumina. 

*  Book  3,  p.  64. 

t  Chymia  Rationalis  ac  Experimentalis. 

X  Observationem  physico-chemicarum  Selectiorium,  1722, 

§  Opusc.  Chim.  de  Marggraff,  I,  p.  8. 

II  Dictionnaire  de  Physique,  Article  "Alun." 


Returning  to  the  time  of  Marggraff,  we  find  soon  after  the 
pubHcation  of  his  paper  indications  that  chemists  suspected 
this  newly-identified  earth  to  be  a  compound  body,  and  the 
search  after  aluminium  had  truly  begun. 

Macquer, *  in  1758,  wrote,  "the  earth  of  alum  is  white,  infus- 
ible, and  I  suspect  that  it  has  a  relation  more  or  less  distant 
with  the  metallic  earths." 

Baron,  f  a  professor  of  chemistry  in  Paris,  is  our  first  re- 
corded experimenter  on  the  isolation  of  aluminium.  In  1760 
he  communicated  a  memoir  to  the  Academy  in  which  he  said : 
"  Marggrafif  of  Berlin  has  shown  us  what  the  earth  of  alum  is 
not,  without  showing  very  definitely  what  it  is.  I  believe  the 
base  of  alum  to  be  of  a  metallic  nature,  for  the  following 
reasons:  i.  It  has  almost  no  properties  in  common  with  the 
known  earths.  2.  It  has  analogies  with  the  metallic  earths,  e.  g., 
its  astringent  salts."  Baron  then  proceeds  to  say  that  he  had 
tried  all  known  methods  of  reducing  this  base,  but  without  re- 
sult, and  concludes  by  saying,  "  If  I  had  been  fortunate  enough 
to  reduce  the  base  of  alum  to  a  metal,  no  other  argument  would 
be  needed,  and  that  which  to-day  I  conjecture  would  be  a  de- 
monstrated fact.  I  am  far  from  regarding  the  problem  as  an 
impossibility.  I  think  it  not  too  venturesome  to  predict  that 
a  day  will  come  when  the  metallic  nature  of  the  base  of  alum 
will  be  incontestably  proven." 

Baron  does  not  record  the  manner  in  which  he  tried  to  re- 
duce alumina,  but  it  is  probable  that  he  mixed  it  with  carbon 
or  some  organic  substance,  with  salt  or  soda  for  flux,  and 
heated  as  highly  as  possible  in  a  charcoal  fire.  We  neverthe- 
less have  his  word  that  he  tried  all  the  methods  of  reduction 
then  known. 

Lavoisier  %  regarded  it  as  highly  probable  that  alumina  was 
the  oxide  of  a  metal,  the  aflSnity  of  the  metal  for  oxygen  being 

*  Memoires  de  Paris,  1758. 

t  Memoires  de  1'  Acad.  Royale,  April  l6,  1760,  p.  274. 

t  Journal  de  Physique,  May,  1782. 


SO  strong  that  neither  carbon  nor  any  of  the  reducing  agents 
then  known  was  able  to  overcome  it. 

Ruprecht  and  Tondi,*  two  Austrian  chemists,  repeated 
Baron's  experiments  in  1790.  They  thought  that  hitherto  the 
reducing  agent  had  not  been  intimately  enough  mixed  with  the 
alumina,  and  that  the  temperature  used  had  not  been  sufficiently 
high,  so  they  mixed  alumina  very  intimately  with  charcoal  dust, 
made  it  into  a  paste  with  oil,  and  spread  it  on  the  inner  walls 
of  a  Hessian  crucible,  which  was  finally  filled  up  with  powdered 
charcoal  and  a  layer  of  bone  ash  placed  on  top.  Putting  the 
crucible  in  a  forge,  a  strong  fire  was  kept  up  for  three  hours. 
As  a  result,  small  metallic  particles  were  found  on  the  inner 
sides  of  the  crucible.  These  they  supposed  to  be  the  metallic 
base  of  alumina. 

Sav4resi,f  in  Italy,  and  Klaproth  and  Karsten,  in  Germany, 
duplicated  this  experiment  with  similar  results,  and  then 
analyzed  the  globules  of  metal  obtained.  They  found  them  to 
be  phosphide  of  iron,  the  iron  coming  from  the  charcoal  used 
and  the  phosphorus  from  the  bone  ash.  Professor  Klaproth 
referred  to  this  incident  as  "  the  pretended  metallization  of  the 
earths,"  and  said  further,  "  if  there  exists  an  earth  which  has 
been  put  in  conditions  where  its  metallic  nature  should  be  dis- 
closed, if  it  had  such,  an  earth  exposed  to  experiments  suitable 
for  reducing  it,  tested  in  the  hottest  fires  by  all  sorts  of 
methods,  on  a  large  as  well  as  on  a  small  scale,  that  earth  is 
certainly  alumina,  yet  no  one  has  yet  perceived  its  metalli- 

Lavoisier  succeeded  in  melting  alumina  in  a  charcoal  fire  fed 
by  pure  oxygen.  Dr.  Hare,  in  1802,  melted  it  with  the  oxy- 
hydrogen  blow- pipe  to  a  white  enamel,  but  noticed  no  signs  of 
reduction  to  metal. 

In  1807  Sir  Humphry  Davy  attacked  the  alkaline  earths 
with  his  great  battery  which  had  isolated  potassium  and  so- 

*  Allgemeiner  Zeitung,  Nov.,  1 790. 
t  Annales  de  Chimie,  1791,  ».,  254. 


dium.  His  first  experiment,  mixing  alumina  with  red  oxide  of 
mercury,  and  passing  the  electric  current  through  this  in  con- 
tact with  metallic  mercury,  gave  no  result.  He  then  melted 
alumina  with  potash,  and  passed  the  current  from  500  plates 
through  it.  The  receiving  blade  received  a  metallic  coating, 
and  on  dipping  it  into  water  the  latter  was  decomposed,  and 
afterwards  the  solution  was  proved  to  contain  alumina.  An 
experiment  with  soda  gave  a  similar  result.  Davy  had  in  fact 
electrolyzed  the  aluminates  of  potassium  and  sodium,  and  ob- 
tained metallic  alkali  and  aluminium,  but  he  was  unable  to 
isolate  the  latter  by  any  means  he  could  devise. 

Davy  next  tried  to  reduce  alumina  by  heating  it  with  metal- 
lic potassium.  Some  potassium  oxide  was  formed,  showing 
some  reduction  had  taken  place,  but  he  could  find  no  metal. 

In  1809  Davy  had  a  new  battery  of  1000  plates,  and  with  it 
fused  iron  to  whiteness  in  the  arc  in  contact  with  alumina. 
The  iron  became  somewhat  whiter,  and  when  dissolved  in  acids 
showed  that  it  contained  aluminium.  The  fact  was  thus  estab- 
lished that  alumina  can  be  decomposed  while  fiuid  in  the  electric 
arc,  and  its  metal  alloyed  with  iron. 

Davy  next  mixed  alumina  with  potassium  and  iron  filings, 
hoping  that  the  iron  would  collect  any  metal  reduced  from  the 
alumina.  On  melting  this  mixture  a  button  resulted  which 
was  white  and  harder  than  iron,  and  was  undoubtedly  an  alloy 
of  iron  and  aluminium,  but  Davy  could  not  separate  the  two 
metals.  In  concluding  the  recital  of  his  experiments  he  said, 
"  Had  I  been  fortunate  enough  to  isolate  the  metal  after  which 
I  sought,  I  would  have  given  it  the  name  alumium. 

In  making  this  suggestion  it  is  perfectly  plain  that  Davy  in- 
tended this  word  to  represent  the  metal  from  alum,  simply 
starting  with  alum,  and  adding  ium  as  the  proper  termination. 
Objections  were  very  soon  thereafter  made  to  this  proposed 
name,  not  to  the  termination  ium,  which  was  considered  abso- 
lutely proper,  but  to  the  root  or  stem  of  the  word.  It  was 
maintained  by  French,  German  and  Swedish  writers  that  the 
name  of  the  new  metal  should  be  derived  from  its  oxide,  and 


that  the  stem  of  the  word  should  therefore  be  alumin,  and 
thence  the  name  aluminium.  Davy  was  influenced  by  these 
criticisms  to  the  extent  of  changing  in  1812  to  alumin-um,  but 
no  writers,  except  a  very  few  English  and,  in  recent  years,  some 
Americans,  have  used  this  spelling. 

Prof.  Benj.  Silliman*  was  in  1813  repeating  Hare's  experi- 
ment of  fusing  alumina  with  the  oxy-hydrogen  blowpipe.  The 
alumina  was  supported  on  charcoal,  and  he  noticed  small  me- 
tallic globules  rolling  and  darting  out  from  under  the  fused 
mass  and  burning  with  a  bright  light.  These  globules  could 
have  been  nothing  else  than  aluminium  reduced  from  fluid 
alumitia  by  charcoal.  The  metal  burnt,  however,  almost  in- 
stantly, and  no  globules  could  be  obtained. 

The  Swedish  chemist  Oersted  believed,  in  1824,  that  he  had 
isolated  aluminium.  He  used  anhydrous  aluminium  chloride 
as  a  starting  point,  and  heated  it  with  potassium  amalgam, 
thinking  that  the  potassium  would  reduce  the  chloride  and 
leave  an  amalgam  of  aluminium  and  mercury,  from  which  the 
latter  could  be  distilled  away.  Potassium,  however,  when 
amalgamated  with  mercury  is  not  powerful  enough  to  reduce 
aluminium  chloride,  although  it  can  reduce  it  if  used  alone,  and 
so  Oersted  missed,  by  a  very  little,  the  honor  of  first  isolating 

Berzelius  was  also  a  worker  on  the  aluminium  problem.  He 
wrote  to  Sir  Humphry  Davy,  in  1809,  that  he  had  reduced 
alumina  by  heating  it  with  carbon  in  the  presence  of  iron,  but 
it  is  probable  that  he  found  himself  mistaken,  as  he  does  not 
refer  to  this  matter  in  any  of  his  later  writings ;  once,  however, 
he  came  within  a  very  little  of  succeeding.  He  had  studied 
the  composition  and  formula  of  the  mineral  cryolite,  had  made 
it  artificially,  and  also  the  corresponding  potassium  salt.  It 
then  occurred  to  him  that  this  latter  salt  might  be  reduced  by 
metaUic  potassium.  He  made  the  experiment  in  a  crucible, 
carefully  washed  the  fusion  with  water,  but  found  no  metal.    It 

*  Memoirs  Connecticut  Acad,  of  Arts  and  Science.     Vol.  I,  1813. 


is  quite  evident  that  his  sole  mistake  was  in  using  an  excess  of 
potassium,  which,  after  the  reduction,  gave  on  sokition  in  water 
a  caustic  alkah  sokition,  which  immediately  dissolved  all  the 
reduced  aluminium.  Had  he  used  an  excess  of  the  fluoride 
salt,  the  story  would  almost  certainly  have  read  difTerently,  be- 
cause this  reduction  has  since  then  been  repeatedly  performed. 
The  date  of  this  experiment  was  1825. 

In  1827,  Frederick  Wohler,  Professor  of  Chemistry  at  the 
University  of  Gottingen,  after  repeating  Oersted's  experiment 
with   unsatisfactory  results,  modified   the  experiment   by  using 


pure  potassium  as  the  reducing  agent,  instead  of  its  amalgam. 
He  obtained  a  grey,  metallic  powder,  which  was  finely-divided 
aluminium.  He  was  unable  to  melt  this  powder  into  a  button, 
so  as  to  determine  its  properties  en  masse,  but  he  described  many 
of  its  chemical  properties,  and  produced  from  it  some  alumin- 
ium compounds  which  had  not  been  before  made,  such  as  the 
sulphide  and  arsenide.  This  powder  was  not  absolutely  pure 
aluminium,  as  it  contained  a  little  platinum  from  the  crucible 
in  which  the  reduction  was  performed,  and  some  potassium, 
which  lessened  its  resistance  to  chemical  agents.     At  that  time 


no  further  use  was  made  of  these  facts.  Later,  in  1845,  on 
making  vapor  of  aluminium  chloride  pass  over  potassium 
placed  in  platinum  boats,  Wohler  obtained  the  metal  in  small 
malleable  globules  of  metallic  appearance,  from  which  he  was 
able  to  determine  the  principal  properties  of  aluminium.  But 
the  metal  thus  obtained  was  scarcely  as  fusible  as  cast  iron, 
without  doubt  because  of  the  platinum  with  which  it  had 
alloyed  during  its  preparation.  In  addition  to  this,  it  decom- 
posed water  at  io6°C,  from  which  we  suppose  that  it  was  still 
impregnated  with   potassium  or  aluminium  chloride.      It  is  to 


H.  St.  Claire  Deville  that  the  honor  belongs  of  having,  in  1854, 
isolated  aluminium  in  a  state  of  almost  perfect  purity,  deter- 
mining its  true  properties. 

Thus,  while  aluminium  had  been  isolated  in  1827,  for 
eighteen  years  its  properties  en  masse  were  unknown,  and  it 
was  only  at  the  end  of  twenty-seven  years  after  its  discovery 
that  the  true  properties  of  the  pure  metal  were  established  by 
Deville.  The  second  birth  of  aluminium,  the  time  at  which  it 
stepped  from  the  rank  of  a  curiosity  into  the  number  of  the 
useful   metals,  dates   from   the   labors  of   Deville    in    1854.     If 


Wohler  was  the  discoverer  of  aluminium,  Deville  was  the 
founder  of  the  aluminium  industry. 

In  commencing  researches  on  aluminium,  Deville,  while  he 
applied  the  method  of  Wohler,  was  ignorant  of  the  latter's  results 
of  1845.  Besides,  he  was  not  seeking  to  produce  aluminium 
that  he  might  turn  its  valuable  properties  to  practical  account, 
but  that  it  might  serve  for  the  production  of  aluminium  prot- 
oxide (AlO),  which  he  believed  could  exist  as  well  as  ferrous 
oxide  (FeO).  The  aluminium  he  wished  to  prepare  would,  he 
thought,  by  its  further  reaction  on  aluminium  chloride,  form 
aluminium  proto-chloride  (AlCP),  from  which  he  might  derive 
the  protoxide  and  other  proto-salts.  But  on  passing  vapor  of 
aluminium  chloride  over  the  metallic  powder  formed  by  reduc- 
tion by  potassium,  this  proto-chloride  was  not  thus  produced; 
he  obtained,  inclosed  in  a  mass  of  aluminium-potassium  chlo- 
ride (AICI3.KCI),  fine  globules  of  a  brilliant  substance,  ductile, 
malleable,  and  very  light,  capable  of  being  melted  in  a  mufifle 
without  oxidizing,  attacked  by  nitric  acid  with  diflSculty,  but 
dissolved  easily  by  hydrochloric  acid  or  caustic  potash  with 
evolution  of  hydrogen. 

Deville  troubled  himself  no  more  about  the  proto-salts  of 
aluminium,  but,  recognizing  the  importance  of  his  discovery, 
turned  his  attention  to  preparing  the  metal.  He  was  at  this 
time  Professor  of  Chemistry  in  the  Ec^le  Normale,  Paris ;  his 
salary  was  but  3000  francs,  his  estate  was  small,  and  he  was 
practically  without  the  means  of  doing  anything  further. 

On  Monday,  February  6,  1854,  Deville  read  at  the  .seance  of 
the  Academy  a  short  paper  entitled  "Aluminium  and  its  Chemi- 
cal Combinations,"  in  which  he  explained  the  results  of  this 
experiment  as  showing  the  true  properties  of  aluminium, 
and  also  furnishing  a  method  of  purifying  it,  and  declared  his 
intention  of  commencing  immediate  search  for  a  process  which 
could  be  economically  applied  on  a  commercial  scale.  M. 
Thenard,  at  the  close  of  the  communication,  remarked  that  such 
experiments  ought  to  be  actively  pursued,  and  that,  since  they 
were  costly,  he  believed  the  Academy  would  hasten  the  accom- 


plishment  of  the  work  by  placing  at  Deville's  disposal  the  neces- 
sary funds.  As  the  outcome  of  this,  the  Academy  appointed 
Deville  one  of  a  committee  to  experiment  on  producing  alumin- 
ium, and  2000  francs  were  placed  at  his  disposal  for  the  work. 

It  was  on  the  occasion  of  the  reading  of  this  paper  that  M. 
Chenot  addressed  a  note  to  the  Academy  on  the  preparation 
of  aluminium  and  other  earthy  and  alkaline  metals,  in  which  he 
claimed,  in  some  regards,  priority  for  his  inventions.  (See 
further  under  "Reduction  by  Carbon.")  This  note  was  re- 
served to  be  examined  by  a  commission  appointed  to  take 
notice  of  all  communications  relative  to  the  production  of 

With  the  funds  thus  placed  at  Deville's  disposal,  he  experi- 
mented at  the  Ecole  Normale  for  several  months.  As  potas- 
sium is  very  dangerous  to  handle,  cost  then  900  francs  a  kilo, 
and  gives  comparatively  but  a  small  return  of  aluminium,  De- 
ville, in  view  of  the  successful  work  of  Bunsen  on  the  electric 
decomposition  of  magnesium  chloride,  tried  first  the  reduction 
of  aluminium  chloride  by  the  battery.  On  March  20,  1854, 
Deville  announced  to  the  Academy  in  a  letter  to  Dumas  that 
he  had  produced  aluminium  without  alkaline  help,  and  sent  a 
leaf  of  the  metal  thus  obtained.  At  that  time  Thenard,  Boussin- 
gault,  Pelouze,  Peligot,  and  later,  de-la-Rive,  Regnault,  and 
other  well-known  scientists,  shared  the  honor  of  assisting  in  the 
laboratory  experiments.  Deville  sent,  in  the  following  May,  a 
mass  of  five  or  six  grammes  weight  to  Liebig,  making  no  secret 
of  the  fact  that  it  was  reduced  by  the  battery ;  while  Balard  at 
the  Sorbonne,  and  Fremy  at  the  Ecole  Polytechnique,  publicly 
repeated  his  experiments  and  explained  them  in  all  their  de- 
tails. Although  these  experiments  succeeded  quite  well,  yet 
because  of  the  large  consumption  of  zinc  in  the  battery  used 
the  process  could  evidently  not  be  applied  industrially,  and 
Deville  felt  obliged  to  return  to  the  use  of  the  alkaline  metals. 

Towards  the  middle  of  1854  Deville  turned  to  sodium,  with- 
out a  knowledge  of  those  properties  which  render  it  so  prefer- 
able to  potassium,  but  solely  because  of  its  smaller  equivalent 


(23  to  that  of  potassium  39)  and  the  greater  cheapness  of  soda 
salts.  He  studied  the  manufacture  of  sodium,  with  the  aid  of 
M.  Debray,  in  his  laboratory  at  the  Ecole  Normale,  and  their 
experiments  were  repeated  at  Rousseau  Bros.'  chemical  works 
at  Glaciere,  when  they  were  so  successful  that  Rousseau  Bros, 
very  soon  put  metallic  sodium  on  the  market  at  a  much  reduced 
price.  It  is  said  that  while  metallic  sodium  was  a  chemical 
curiosity  in  1855,  costing  something  like  2000  francs  a  kilo,  its 
cost  in  1859  is  put  down  at  10  francs.  Deville  carried  this  pro- 
cess to  such  perfection  that  for  twenty-five  years  it  remained 
almost  precisely  at  the  status  in  which  he  left  it  in  1859.  In 
order  to  still  further  cheapen  aluminium,  Deville  busied  himself 
with  the  economic  production  of  alumina,  which  gave  later  a 
lively  impulse  to  the  cryolite  and  bauxite  industries. 

On  August  14,  1854,  Deville  read  a  paper  before  the  Acad- 
emy describing  his  electrolytic  methods  at  length  (see  under 
"Reduction  by  Electricity"),  showing  several  small  bars  of  the 
metal,  and  also  stating  some  of  the  results  already  achieved  by 
the  use  of  sodium,  but  not  going  into  details,  since  he  believed 
that  numerous  analyses  were  necessary  to  confirm  these  results 
— which  he  was  unable  to  have  made  with  the  funds  at  his  dis- 
posal. He  also  stated  that  the  desire  to  show,  in  connection 
with  his  assertions,  interesting  masses  of  the  metal,  alone  pre- 
vented the  earlier  publication  of  the  methods  used.  Several 
days  before  this,  Bunsen  published  in  Poggendorif's  Annalen 
a  process  for  obtaining  aluminium  by  the  battery,  which  re- 
sembled Deville's  method,  but  of  which  the  latter  was  ignorant 
when  he  read  his  paper.  Thus  it  is  evident  that  the  isolation 
of  aluminium  by  electrolysis  was  the  simultaneous  invention  of 
Deville  and  Bunsen. 

After  reading  this  paper,  Deville  caused  a  medal  of  alumin- 
ium to  be  struck,  which  he  presented  to  the  Emperor  Na- 
poleon III.  The  latter,  looking  forward  to  applying  such  a 
light  metal  to  the  armor  and  hemlets  of  the  French  Cuirassiers, 
immediately  authorized  experiments  to  be  continued  at  his  own 
expense  on  a  large  scale.     This  anticipation  ultimately  proved 


impracticable,  but  the  ambition  in  which  it  was  bred  was  caused 
for  once  to  minister  to  the  lasting  benefit  of  mankind.  Deville, 
however,  about  this  time  accepted,  in  addition  to  his  duties  as 
professor  at  the  Ecole  Normale,  a  lectureship  at  the  Sorbonne 
(where  he  afterwards  obtained  a  full  professorship),  and  it  was 
not  until  March  of  the  next  year  that  the  experiments  at  the 
cost  of  the  Emperor  were  begun. 

It  was  about  August,  1854,  that  two  young  chemists,  Chas. 
and  Alex.  Tissier,  at  the  suggestion  of  Deville,  persuaded  M. 
de  Sussex,  director  of  a  chemical  works  at  Javel,  to  let  them 
experiment  in  his  laboratory  (of  which  they  had  charge)  on 
the  production  of  sodium. 

Towards  the  commencement  of  1855,  Deville  took  up  the  in- 
dustrial question,  the  Emperor  putting  at  his  disposition  all  the 
funds  necessary  for  the  enterprise,  and  in  March  the  investigator 
went  to  work  and  installed  himself  at  the  chemical  works  at 
Javel  in  a  large  shed  which  the  director,  M.  de  Sussex,  kindly 
put  at  his  service. 

The  investigations  were  carried  on  here  for  nearly  four 
months,  ending  June  29th,  and  the  process  elaborated  was  an 
application  on  a  large  scale  of  the  experiments  he  had  made  at 
the  expense  of  the  Academy,  which  he  described  in  his  paper 
of  August  14,  1854,  and  by  which  he  had  been  able  to  obtain 
a  few  pencils  of  metal.  In  this  work  such  success  attended  his 
efforts  that  on  June  18  Deville  presented  to  the  Academy 
through  M.  Dumas  large  bars  of  pure  aluminium,  sodium,  and 
masses  of  aluminium  chloride.  The  members  and  large  audi- 
ence were  loud  in  their  admiration  and  surprise  at  the  beauty 
of  the  metal.  Dumas  stated  that  the  experiments  at  Javel  had 
put  beyond  a  doubt  the  possibility  of  extracting  aluminium  on 
a  large  scale  by  practical  processes.  Deville's  paper  was  then 
read,  describing  all  his  processes  in  detail,  and  concluding  with 
the  following  words :  "  After  four  months  of  work  on  a  large 
scale,  undertaken  without  responsibility  on  my  part,  and,  in 
consequence  with  the  tranquility  and  repose  of  mind  which  are 
so  often  wanting  to  the  investigator,  without  the  preoccupation 


of  expense,  borne  by  His  Majesty  the  Emperor,  whose  gen- 
erosity had  left  me  entire  liberty  of  action,  encouraged  each 
day  by  distinguished  men  of  science,  I  hope  to  have  placed  the 
aluminium  industry  on  a  firm  basis." 

It  was  the  metal  made  at  this  time  at  Javel  which  was  ex- 
hibited at  the  Paris  Exposition  in  1855.  In  the  Palais  de  I'ln- 
dustrie,  among  the  display  from  the  porcelain  works  at  Sevres, 
were  ingots  and  some  manufactured  objects.  The  first  article 
made  of  aluminium  was,  in  compliment  to  the  Emperor,  a  baby- 
rattle  for  the  infant  Prince  Imperial,  for  which  purpose  it  must 
have  served  well,  because  of  the  sonorousness  of  the  metal. 

After  terminating  these  experiments  Deville  continued  work- 
ing at  the  Ec61e  Normale,  the  Emperor  defraying  his  expenses, 
until  April,  1856.  The  memoir  published  in  the  Ann.  de  Chim. 
et  de  Phys.,  April,  1856,  contains,  besides  the  results  obtained 
at  Javel,  the  improvements  devised  in  the  meantime. 

It  appears  that  when  Deville  first  went  to  Javel,  he  had  for 
assistants  the  Tissier  Brothers,  who  were  charged  by  M.  de 
Sussex  to  give  him  all  the  aid  they  could.  Since  the  previous 
autumn  the  Tissiers  had  been  experimenting  on  sodium  fur- 
naces, and  now,  in  concert  with  Deville,  they  drew  up  plans  for 
furnaces,  and  aided  in  devising  other  apparatus.  Under  these 
circumstances  the  furnace  for  the  continuous  manufacture  of 
sodium  in  cylinders  was  devised,  which  the  Tissiers  claim  De- 
ville strongly  advised  them  to  make  their  property  by  patenting, 
asking  only  from  them  the  use  of  it  for  his  experiments.  So, 
immediately  after  the  experiments  were  ended,  in  July,  the 
Tissiers  patented  the  furnace  in  question,  and,  leaving  Paris, 
took  charge  of  M.  Chanu's  works  at  Rouen.  On  the  other 
hand,  Deville  always  reproached  them  for  acting  in  bad  faith. 
He  says  that  after  having  assisted  for  about  two  months  in  set- 
ting up  his  apparatus,  being  forced  to  leave  the  works  because 
of  misunderstandings  between  them  and  M.  de  Sussex,  they 
were  admitted  to  his  laboratory  at  the  Ecole  Normale,  and 
initiated  by  him  into  the  knowledge  of  all  those  processes 
which  they  made  use  of  afterwards,  then  suddenly  left,  taking 


drawings  of  furnaces,  details  of  processes,  etc.,  which  they  not 
only  made  free  use  of,  but  even  patented.  However,  whichever 
party  was  in  the  right  (and  those  who  comprehend  the  char- 
acter of  Deville  can  hardly  doubt  which  was),  the  fact  stands 
that  in  July,  1855,  M.  Chanu,  an  honorable  manufacturer  of 
Rouen,  founded  a  works  in  which  Deville's  processes  were  to 
be  applied,  and  intrusted  the  direction  of  it  to  the  Tissier 

The  history  of  the  works  at  Rouen  is  thus  described  by  the 
Tissiers  in  their  book  on  aluminium,  of  which  we  shall  speak  a 
little  further  on : 

"la  July,  185s,  Messrs.  Maletra,  Chanu,  and  Davey,  of 
Rouen,  formed  a  company  to  produce  aluminium,  and  we  were 
intrusted  with  the  organization  and  special  charge  of  the  in- 
dustry. The  commencement  was  beset  with  difficulties,  not 
only  in  producing,  but  in  using  the  metal.  It  then  sold  at  $200 
per  kilo,  the  price  being  an  insurmountable  obstacle  to  its  em- 
ployment in  the  arts.  The  small  capital  at  our  disposal  was 
not  enough  to  start  the  industry,  to  pay  general  expenses,  and 
the  losses  occasioned  by  the  many  experiments  necessary.  On 
February  28,  1856,  the  society  was  dissolved.  In  April  of  the 
same  year,  M.  William  Martin,  struck  by  the  results  already 
obtained  and  sanguine  of  greater  success,  united  with  us.  From 
that  time  daily  improvements  confirmed  M.  Martin's  hopes, 
and  in  1857  the  works  at  Amfreville-la-mi-Voie,  near  Rouen, 
sold  the  metal  at  $60  per  kilo  ($2  per  oz.).  The  laboratory 
of  this  works  was  devoted  to  researches  on  everything  concern- 
ing the  production  and  application  of  aluminium.  M.  Martin 
has  our  sincere  gratitude  for  the  kindness  with  which  he  so 
willingly  encouraged  and  contributed  to  the  progress  of  the 
manufacture  of  this  wonderful  metal." 

The  process  ultimately  used  at  Amfreville  was  the  reduction 
of  cryolite  by  sodium,  but  the  enterprise  was  not  a  permanent 
success,  and  after  running  for  a  few  years  it  was  abandoned  and 
the  works  closed. 

Returning  to  Deville,  we  find  that  after  leaving  Javel  one  of 


the  first  subjects  he  investigated  was  the  use  of  cryolite  for 
producing  aluminium.  The  researches  made  with  the  aid  of 
MM.  Morin  and  Debray  were  published  in  the  memoir  of  April, 
1856,  and  became  the  basis  of  the  process  carried  out  by  the 
Tissiers  at  Rouen.  Besides  this,  Deville  perfected  many  of  the 
details  of  a  practical  aluminium  plant,  with  the  result  that  in 
the  spring  of  1856  he  united  with  Messrs.  Debray,  Morin,  and 
Rousseau  Bros,  (the  latter  manufacturers  of  chemicals  at  Gla- 
ciere,  in  whose  works  aluminium  had  been  made  since  the 
middle  of  1855)  and  put  up  new  apparatus  in  the  works  at 
Glaciere,  the  company  furthering  the  work  entirely  at  their  own 
cost.  This  enterprise  lasted  for  more  than  a  year,  during  which 
a  number  of  processes  were  tried  and  continued  improvements 
made,  so  that  towards  August  of  the  same  year  aluminium 
was  put  on  the  market  in  Paris  at  300  francs  a  kilo,  being  one- 
third  what  it  cost  a  year  previous. 

Finally,  in  April,  1857,  the  little  works  at  Glaciere,  a  suburb 
of  Paris,  in  the  midst  of  gardens  and  houses,  and  turning  into 
the  air  fumes  charged  with  chlorine  and  salts,  was  obliged  by 
reason  of  general  complaints  to  stop  making  aluminium.  The 
plant  was  moved  to  Nanterre,  where  it  remained  for  some  years, 
under  the  direction  of  M.  Paul  Morin,  being  on  a  scale  four 
times  as  large  as  the  actual  demand.  Afterwards  part  of  the 
plant  was  moved  to  the  works  of  H.  Merle  &  Co.,  at  Salindres, 
and  later  on  the  whole  plant,  where  the  manufacture  was  until 
recently  carried  on  by  Pechiney  &  Co.  The  works  at  Nan- 
terre were  really  the  only  "aluminium  works"  built  by  Deville, 
the  others  were  plants  installed  at  general  chemical  works  ;  but 
these  at  Nanterre  were  built  by  the  united  efforts  of  Deville, 
his  brothers  and  parents,  and  a  few  personal  friends.  Among 
those  who  aided  Deville,  especially  in  the  problems  which  the 
new  industry  presented,  he  speaks  warmly  of  Messrs.  d'Eichtal, 
Lechatelier,  and  Jacquemont. 

In  1858  the  Tissiers  wrote  and  published-  a  small  work 
entitled  "  Recherches  sur  1' Aluminium."  which,  in  view  of  what 
Deville  could  have  written  about  the  subject,  was  a  decided 


misrepresentation  of  the  results  which  had  been  thus  far  accom- 
plished. Deville  thought  that  the  industry  was  yet  too  young 
to  merit  any  sort  of  publication,  yet  he  naively  writes  in  his 
work  "De  1'  Aluminium,"  in  1859,  "I  will  sincerely  acknowl- 
edge that  my  writing  is  a  little  due  to  my  pride,  for  I  decided 
to  take  the  pen  to  speak  of  my  work,  only  to  avoid  seeing  it 
belittled  and  disfigured  as  it  has  been  lately  in  the  book  written 
by  MM.  Tissier." 

Deville  published  his  book  in  September,  1859,  and  he  con- 
cludes it  with  these  words :  "  I  have  tried  to  show  that  alumin- 
ium may  become  a  useful  metal  by  studying  with  care  its 
physical  and  chemical  properties,  and  showing  the  actual  state 
of  its  manufacture.  As  to  the  place  which  it  may  occupy  in 
our  daily  life,  that  will  depend  on  the  public's  estimation  of  it 
and  its  commercial  price.  The  introduction  of  a  new  metal 
into  the  usages  of  man's  life  is  an  operation  of  extreme  diffi- 
culty. At  first  aluminium  was  spoken  of  too  highly  in  some 
publications,  which  made  it  out  to  be  a  precious  metal,  but 
later  these  estimates  have  depreciated  even  to  the  point  of  con- 
sidering it  attackable  by  pure  water.  The  cause  of  this  is  the 
desire  which  many  have  to  see  taken  out  of  common  field-mud 
a  metal  superior  to  silver  itself ;  the  opposite  opinion  established 
itself  because  of  very  impure  specimens  of  the  metal  which  were 
put  in  circulation.  It  seems  now  that  the  intermediate  opinion, 
that  which  I  have  always  held  and  which  I  express  in  the  first 
lines  of  my  book,  is  becoming  more  public,  and  will  stop  the 
illusions  and  exaggerated  beliefs  which  can  only  be  prejudicial 
to  the  adoption  of  aluminium  as  a  useful  metal.  Moreover, 
the  industry,  established  as  it  now  is,  can  be  the  cause  of  loss 
to  no  one ;  as  for  myself,  I  take  no  account  of  the  large  part  of 
my  estate  which  I  have  devoted,  but  am  only  too  happy  if  my 
efforts  are  crowned  with  definite  success,  in  having  made  fruit- 
ful the  works  of  a  man  whom  I  am  pleased  to  call  my  friend, 
the  illustrious  Wohler." 

Contemporary  with  the  early  labors  of  Deville,  among  the 
numerous  chemists  and  metallurgists  investigating  this  attract- 


ive  field,  we  find  Dr.  Percy  in  England  and  H.  Rose  in  Ger- 
many, whose  experiments  on  the  reduction  of  cryolite  by 
sodium  were  quite  successful,  and  are  herein  described  later  on. 

As  early  as  1856  we  find  an  article  in  an  American  magazine  * 
showing  that  there  were  already  chemists  in  the  United  States 
spending  time  and  money  on  this  subject.  The  following  is  the 
substance  of  the  article  alluded  to:  "Within  the  last  two  years 
Deville  has  extracted  50  to  60  lbs.  of  aluminium.  At  the  pres- 
ent time,  M.  Rousseau,  the  successor  of  Deville  in  this  manu- 
facture, produces  aluminium  which  he  sells  at  $100  per  pound. 
No  one  in  the  United  States  has  undertaken  to  make  the  metal 
until  recently  Mons.  Alfred  Monnier,  of  Camden,  N.  J.,  has, 
according  to  the  statement  of  Prof.  James  C.  Booth  in  the 
"  Penn.  Inquirer,"  been  suceessful  in  making  sodium  by  a  con- 
tinuous process,  so  as  to  procure  it  in  large  bars,  and  has  made 
aluminium  in  considerable  quantity,  specimens  of  which  he  has 
exhibited  to  the  Franklin  Institute.  Mons.  Monnier  is  desirous 
of  forming  a  company  for  the  manufacture  of  aluminium,  and  is 
confident  that  by  operating  in  a  large  way  he  can  produce  it  at 
a  much  less  cost  than  has  heretofore  been  realized.  We  would 
suggest  the  propriety  of  giving  aid  to  this  manufacture  at  the 
expense  of  the  government,  for  the  introduction  of  a  new  metal 
into  the  arts  is  a  matter  of  national  importance,  and  no  one  can 
yet  realize  the  various  and  innumerable  uses  to  which  this  new 
metal  may  be  applied.  It  would  be  quite  proper  and  constitu- 
tional for  Congress  to  appropriate  a  sum  of  money,  to  be  ex- 
pended under  the  direction  of  the  Secretary  of  the  Treasury  in 
the  improvement  of  this  branch  of  metallurgy,  and  in  testing 
the  value  of  the  metal  for  coinage  and  other  public  use." 

In  the  next  volume  of  the  "Mining  Magazine"!  there  is  a 
long  article  by  Mr.  W.  J.  Taylor,  containing  nothing  new  in 
regard  to  the  metallurgy  of  aluminium,  but  chiefly  concerned 
in  calculating  theoretically  the  cost  of  the  metal  from  the  raw 

*  Mining  Magazine,.  1856,  vii.,  317. 

t  Mining  Magazine,  viii.,  167  and  228.     Proc.  Ac.  Nat.  Sci.,  Jan.,  1857. 


materials  and  labor  required  by  Deville's  processes,  and  con- 
cluding that  it  was  quite  possible  to  make  it  for  $  i  .00  per  pound. 

In  1859  the  first  aluminium  works  in  England  were  started  at 
Battersea,  near  London,  by  C.  H.  Gerhart,  using  Deville's  pro- 
cess. No  details  are  obtainable  respecting  the  size  of  this 
works.  M.  Henri  Brivet  informs  me  that  they  had  no  connec- 
tion with  Bell  Bros.'  enterprise,  started  the  next  year  after,  and 
that  they  closed  operations  about  1865. 

In  i860,  Bell  Bros,  established  a  plant  at  Washington,  near 
Newcastle-on-Tyne,  with  the  immediate  co-operation  of  Deville.' 
In  1862  this  company  was  selling  aluminium  at  40  shiUings  per 
troy  pound,  and  they  continued  operations  until  1874,  when 
they  closed  because  the  business  was  no  longer  profitable.* 

It  was  probably  shortly  after  1 874  that  the  large  firm  of  J.  F. 
Wirtz  &  Co.,  Berlin,  made  an  attempt  to  start  an  aluminium 
works.  The  project  drooped  before  it  was  well  started ;  and  it 
is  only  within  the  last  few  years  that  Germany  has  possessed  a 
flourishing  aluminium  industry. 

The  further  we  get  away  from  an  age  the  better  able  are  we 
to  write  the  true  history  of  that  age.  And  so  as  years  pass 
since  the  labors  of  Wohler,  Deville,  and  Tissier,  we  are  now 
able  to  see  better  the  whole  connected  history  of  the  develop- 
ment of  this  art.  Dr.  Clemens  Winckler  gives  us  a  compre- 
hensive retrospect  of  the  field  seen  from  the  standpoint  of  1879, 
from  which  we  condense  the  following :  -j-  "  The  history  of  the 
art  of  working  in  aluminium  is  a  very  short  one,  so  short  that 
the  present  generation  with  which  it  is  contemporary  is  in  dan- 
ger of  overlooking  it  altogether.  The  three  international  exhi- 
bitions which  have  been  held  in  Paris  since  aluminium  first 
began  to  be  made  on  a  commercial  scale  form  so  many  memo- 
rials of  its  career,  giving  as  they  did  at  almost  equal  intervals 
evidence  of  the  progress  made  in  its  application.  In  1855  we 
meet  for  the  first  time  in  the  Palais  de  1' Industrie  with  a  large 

*  Personal  communication  to  the  writer  from  Sir  Lowthian  Bell, 
t  Industrie  Blatter,  1879;  Sci.  Am.  Suppl.,  Sept.  6,  1879. 


bar  of  the  wonderful  metal,  docketed  with  the  extravagant 
name  of  the  '  silver  from  clay.'  In  1 867  we  meet  with  it  again 
worked  up  in  various  forms,  and  get  a  view  of  the  many  diffi- 
culties which  had  to  be  overcome  in  producing  it  on  a  large 
scale,  purifying  and  moulding  it.  We  find  it  present  as  sheets, 
wire,  foil,  or  worked-up  goods,  polished,  engraved,  and  soldered, 
and  see  for  the  first  time  its  most  important  alloy,  aluminium 
bronze.  After  a  lapse  of  almost  another  dozen  years  we  see  at 
the  Paris  Exhibition  of  1878  the  maturity  of  the  industry.  We 
have  passed  out  of  the  epoch  in  which  the  metal  was  worked 
up  in  single  specimens,  showing  only  the  future  capabilities  of 
the  metal,  and  we  see  it  accepted  as  a  current  manufacture 
having  a  regular  supply  and  demand,  and  being  in  some  re- 
gards commercially  complete.  The  despair  which  has  been 
indulged  in  as  to  the  future  of  the  metal  is  thus  seen  to  have 
been  premature.  The  manufacture  of  aluminium  and  goods 
made  of  it  has  certainly  not  taken  the  extension  at  first  hoped 
for  in  its  behalf ;  the  lowest  limit  of  the  cost  of  manufacture  was 
soon  reached,  and  aluminium  remains  as  a  metal  won  by  ex- 
pensive operations  from  the  cheapest  of  raw  materials. 

"  There  are  several  reasons  why  the  metal  is  shown  so  little 
favor  by  mathematical  instrument  makers  and  others.  First  of 
all,  there  is  the  price ;  then  the  methods  of  working  it  are  not 
everywhere  known ;  and  further,  no  one  knows  how  to  cast  it. 
Molten  aluminium  attacks  the  common  earthen  crucible,  re- 
duces silicon  from  it,  and  becomes  gray  and  brittle.  This 
inconvenience  is  overcome  by  using  lime  crucibles,  or  by  lining 
an  earthen  crucible  with  carbon  or  strongly  burnt  cryoHte  clay. 
If  any  one  would  take  up  the  casting  of  aluminium  and  bring  it 
into  vogue  as  a  current  industrial  operation,  there  is  no  doubt 
that  the  metal  would  be  more  freely  used  in  the  finer  branches 
of  practical  mechanics." 

At  the  time  of  Dr.  Winckler's  writing,  the  extraction  of 
aluminium  in  France  was  carried  on  by  Merle  &  Co.,  at  Salin- 
dres,  while  the  Societe  Anonyme  de  1' Aluminium,  at  Nanterre, 
worked  up  the  metal.     Both  firms  were  represented  at  the  Ex- 


position  of  1878.  The  prices  quoted  then  were  130  francs  a 
kilo  for  aluminium,  and  18  francs  for  10  per  cent,  aluminium 
bronze.  From  1874,  when  Bell  Bros.'  works  at  Newcastle-on- 
Tyne  stopped  operations,  until  1882,  when  a  new  enterprise 
was  started  in  England  by  Mr.  Webster,  the  French  company 
were  the  only  producers  of  aluminium. 

Regarding  the  prospects  of  the  aluminium  industry  at  this 
period,  we  can  very  appropriately  quote  some  remarks  of  the 
late  Mr.  Walter  Weldon,  F.  R.  S.,  who  was  a  personal  friend  of 
M.  Pechiney  (director  of  the  works  at  Salindres),  had  given 
great  attention  to  aluminium,  and  was  considered  as  a  first 
authority  on  the  subject.  Speaking  in  March,  1883,  before  the 
London  Section  of  the  Society  of  Chemical  Industry,  he  stated 
that  the  only  method  then  practiced  for  the  manufacture  of 
aluminium  was  DeviUe's  classical  one;  that  at  Salindres,  M. 
Pechiney  had  improved  and  cheapened  it,  but  that  was  all  the 
progress  made  in  the  industry  in  twenty-five  years.  Continu- 
ing, Mr.  Weldon  outlined  the  possible  lines  on  which  improve- 
ments might  be  made,  as  : 

1st.  Cheapening  the  production  of  aluminium  chloride,  or  of 
aluminium-sodium  chloride. 

2d.  Substituting  for  these  chlorides  some  other  cheaper 
anhydrous  compounds  of  aluminium  not  containing 

3d.    Cheapening  sodium. 

4th.  Replacing  sodium  by  a  cheaper  reducing  agent. 

Mr.  Weldon  exhibited  the  relative  cost  of  the  materials  used 
in  making  aluminium,  as  then  carried  on  by  M.  Pechiney,  as : 

Producing  the  alumina 10  per  cent. 

"  "     double  chloride 33        " 

"  "     sodium  and  reducing  therewith 57        " 

"Discussing  these  figures,  it  is  seen  that  the  cost  of  the  alu- 
mina forms  but  a  small  item  in  the  cost  of  the  metal,  since  a 
saving  of  50  per  cent,  in  its  cost  would  only  cheapen  the  metal 
5  per  cent.     A  large  margin  is,  however,  left  in  the  conversion 


of  the  alumina  into  the  chloride,  and  it  is  here  that  a  large  sav- 
ing may  be  expected,  either  in  cheaper  methods  of  producing 
the  chloride  or  by  the  substitution  of  some  other  cheaper  salt 
for  the  chloride.  The  only  other  suitable  compounds  which 
might  replace  the  latter  are  the  fluoride,  iodide,  bromide,  sul- 
phide, phosphide,  or  cyanide.  The  fluoride  has  been  used  to 
some  extent  in  the  form  of  cryolite,  but,  from  the  impurities  in 
the  mineral  and  its  corrosive  action  on  the  apparatus  used  for 
reduction,  the  metal  produced  is  very  much  contaminated  with 
iron  and  silicon.  The  bromide  and  iodide,  no  matter  how  pro- 
duced, would  always  be  too  costly  to  replace  the  chloride.  The 
production  of  the  sulphide  in  a  suitable  form  from  which  the 
metal  can  be  extracted  has  thus  far  not  proved  a  success,  and 
even  if  ever  it  be  thus  produced  in  a  suitable  condition,  it  is  not 
at  all  likely  to  be  as  cheap  a  material  to  use  as  the  chloride. 
The  phosphide  and  cyanide  can  thus  far  only  be  produced  from 
the  metal  itself,  and  are,  therefore,  totally  out  of  the  question. 
To  find  a  substitute  for  sodium  as  a  reducing  agent  has  been  a 
favorite  object  of  research  among  chemists  for  the  past  thirty 
years,  and  although  every  element  occurring  in  any  abundance, 
or  obtainable  at  a  cheaper  rate  than  sodium,  has  been  tried 
under  almost  all  conditions,  yet  absolutely  nothing  has  been 
accomplished  in  this  direction  that  would  entitle  any  one  to  the 
belief  that  aluminium  can  ever  be  produced  chemically  without 
the  use  of  sodium.  So  absorbing  to  those  interested  in  the 
search  for  a  substitute  for  sodium  has  the  occupation  proved, 
that  the  effort  to  cheapen  sodium  did  not  receive  anything  like 
its  fair  share  of  attention.  Since  of  the  57  per  cent,  ascribed 
to  the  cost  of  sodium  and  reduction,  50  per  cent,  represents  the 
sodium,  which  thus  costs  about  six  shillings  a  pound,  there  is 
seen  to  be  a  very  large  margin  for  improvements,  since  the  raw 
materials  for  a  pound  of  sodium  do  not  cost  over  i  or  at  most 
2  shillings." 

In  1882  the  cost  of  aluminium  was  materially  cheapened  by 
the  applications  of  the  inventions  of  Mr.  Webster,  which,  in  ac- 
cordance with  the  analysis  of  the  problem  made  by  Mr.  Weldon, 


consisted  principally  in  the  cheap  production  of  alumina  and  its 
conversion  into  chloride.  Mr.  Webster  had  experimented  on 
this  subject  many  years,  and  in  1881  and  1882  took  out  patents 
for  his  processes,  and  organized  the  "Aluminium  Crown  Metal 
Company,"  located  at  Hollywood,  near  Birmingham,  where 
several  thousand  pounds  were  expended  in  plant.  Business 
was  soon  commenced  on  a  large  scale,  the  company  produc- 
ing, however,  many  other  alloys  besides  those  of  aluminium. 
The  business  grew  until  it  soon  became  the  serious  competitor 
of  the  French  company,  and  practically  controlled  the  English 
market.  However,  a  radical  change  of  still  greater  importance 
in  the  sodium  process  was  made  in  1886  by  an  invention  of 
Mr.  H.  Y.  Castner,  of  New  York  City.  This  gentleman  con- 
ceived the  plan  of  reducing  sodium  compounds  in  cast-iron 
pots,  from  a  fused  bath  of  caustic  soda,  by  which  the  reduction 
is  performed  at  a  much  lower  temperature,  and  the  yield  of 
sodium  is  very  much  more  than  by  the  Deville  method.  The 
application  of  this  process  on  a  large  scale,  with  the  use  of  gas 
furnaces  and  other  modern  improvements,  has  lowered  the  cost 
of  sodium  from  $1  per  pound  to  about  20  or  25  cents.  It  is 
but  just  to  say  that  Mr.  Castner's  invention  was  by  no  means  a 
chance  discovery.  For  four  years  he  worked  in  a  large  labor- 
atory fitted  up  for  this  special  purpose,  and  after  many  dis- 
couragements in  trying  to  produce  aluminium  by  means  other 
than  that  of  sodium,  was  led  finally  to  consider  that  the  cheap- 
ening of  this  metal  was  the  most  promising  method  for  cheap- 
ening aluminium,  and  after  much  patient,  hard  work,  success 
was  at  last  reached. 

Mr.  Castner's  patent  was  taken  out  in  the  United  States  in 
June,  1 886,  and,  while  being  the  first  one  granted  on  that  sub- 
ject in  this  country,  is  said  also  to  be  the  only  one  taken  out  in 
the  world  since  1808.  With  the  assistance  of  Messrs.  J.  H.  and 
Henry  Booth,  of  New  York  City,  Mr.  Castner  demonstrated  the 
process  by  building  and  operating  a  furnace  on  a  somewhat 
large  scale.  This  being  accomplished,  Mr.  Castner  crossed  to 
England  and  met  the  representatives  of  the  Webster  process. 


with  whom  it  was  evident  a  combination  would  be  especially 
advantageous  to  both  parties ;  for,  with  cheap  aluminium  chlor- 
ide and  cheap  sodium,  it  was  clear  that  a  strong  process  could 
be  built  up.  Mr.  Castner  then  demonstrated  plainly,  by  erect- 
ing a  furnace  and  operating  it  for  several  weeks,  that  his  pro- 
cess was  all  that  he  claimed  for  it.  As  a  result  of  this  success, 
the  "Aluminium  Company,  Limited,"  was  incorporated  in  June, 
1887,  with  a  share  capital  of  .£'400,000,  "  to  acquire  the  patents 
and  work  and  develop  the  inventions  of  James  Webster  for  the 
manufacture  of  pure  alumina  and  certain  metallic  alloys  and 
compounds,  together  with  the  business  at  present  carried  on  by 
the  Webster  Patent  Aluminium  Crown  Metal  Company,  Lim- 
ited, in  Birminghami,  Sheffield,  and  London,  England,  and  also 
to  acquire  the  patents  and  work  and  develop  the  invention  of 
H.  Y.  Castner  for  the  manufacture  of  sodium  and  potassium." 
Mr.  Webster  was  paid  ;£'2 30,000  for  the  business,  properties, 
stock,  etc.,  of  the  Crown  Metal  Company,  while  ;£'i40,ooo  was 
allowed  for  the  sodium  patents.  The  new  company  appointed 
Mr.  Castner  managing  director,  and  the  erection  of  large  works 
was  immediately  begun  at  Oldbury,  near  Birmingham.  These 
works  were  started  in  operation  at  the  end  of  July,  1888.  They 
covered  five  acres  of  ground,  and  their  daily  production  for 
some  time  was  about  250  pounds,  which  was  sold  at  20  s.  per 
pound.  This  was  increased  during  1889  to  nearly  500  pounds 
a  day,  and  the  selling  price  of  the  aluminium  decreased  to  16 
shillings.  Early  in  1891,  however,  this  company  was  forced  to 
stop  the  manufacture  of  aluminium,  as  its  selling  price  was  re- 
duced by  the  owners  of  the  electrolytic  processes  below  4  shil- 
lings per  pound,  at  which  price  the  sodium  processes  could  no 
longer  compete.  The  company  continued  in  the  sodium  busi- 
ness, and  in  1893,  with  their  original  capital  of  .£400,000  writ- 
ten down  to  ;£^8o,ooo,  we  hear  that  they  are  doing  a  prosperous 
business  under  Mr.  Castner's  direction,  producing  sodium  and 
sodium  peroxide,  and  making  caustic  soda  and  bleaching 
powder  by  electrolysis  of  common  salt.  In  view  of  the  promi- 
nent part  which  this  works  took  in  the  aluminium  industry  from 


1888  to  1 89 1,  and  as  an  acknowledgment  to  Mr.  Castner's  able 
direction,  the  methods  there  used  have  been  rightly  designated 
as  "  The  Deville-Castner  Process." 

We  have  followed  the  progress  of  the  Webster  and  Castner 
processes  up  to  the  date  of  starting  the  works  at  Oldbury,  be- 
cause the  continuity  of  the  advances  made  in  the  old  Deville 
process  would  hardly  allow  of  a  break  in  order  to  mention 
other  processes  arising  meanwhile.  However,  the  years  since 
1884  have  witnessed  not  one  but  several  revolutions  in  the  alu- 
minium industry.  The  great  advances  made  in  dynamo-electric 
machinery  in  the  last  decade  have  led  to  the  revival  of  the  old 
methods  of  electrolysis  descovered  by  Deville  and  Bunsen,  and 
to  the  invention  of  new  methods  of  decomposing  aluminium 
compounds  electrolytically.  It  will  be  recalled  that  the  first 
small  pencils  of  aluminium  made  by  Deville  were  obtained  by 
electrolysis,  and  that  he  turned  back  to  the  use  of  the  alkaline 
metals  solely  because  the  use  of  the  battery  to  effect  the  de- 
composition was  far  too  costly  to  be  followed  industrially. 
This  fact  still  holds  true,  and  we  cannot  help  supposing  that  if 
Deville  had  had  dynamos  at  his  command  such  as  we  have  at 
present,  the  time  of  his  death  might  have  seen  the  aluminium 
industry  far  ahead  of  where  it  now  is. 

First  in  point  of  time  we  notice  Gratzel's  process,  patented  in 
Germany  in  1883  and  used  industrially  by  the  "Aluminium  and 
Magnesium  Fabrik,  Patent  Gratzel,"  at  Hemelingen,  near  Bre- 
men. The  process  was  essentially  the  electrolysis  of  a  bath  of  a 
fused  aluminium  salt,  such  as  chloride  or  fluoride,  the  improve- 
ments on  the  older  experiments  being  in  details  of  apparatus 
used,  the  use  especially  of  anodes  of  mixed  carbon  and  alu- 
mina, and  the  use  of  dynamic  electricity.  Several  metallurgists 
maintained  the  uselessness  of  the  Gratzel  processes,  and  their 
position  was  proved  to  be  not  far  from  the  truth,  for  in  October, 
1887,  the  company  announced  that  the  addition  "  Pt.  Gratzel" 
would  be  dropped  from  the  firm  name,  since  they  had  aban- 
doned Gratzel's  processes  and  were  making  aluminium  by 
methods  devised  by  Herr  Saarburger,  director  of  their  works. 


The  processes  of  this  latter  gentleman  not  being  published,  we 
are  unable  to  state  their  nature,  but  they  were  very  probably 
electrolytic.  In  October,  1888,  Mr.  Saarburger  reported  that 
their  works  were  producing  at  the  rate  of  12,000  kilos  of  alu- 
minium yearly,  besides  a  large  quantity  of  aluminium  bronze 
and  ferro-aluminium.  The  firm  also  worked  up  the  aluminium 
and  its  alloys  into  sheet,  wire,  tube,  etc. 

Since  1890,  however,  this  company  has  retired  from  the  alu- 
minium business,  their  works  being  now  used  only  for  the  pro- 
duction of  magnesium. 

A  somewhat  similar  electrolytic  process  was  patented  by  Dr. 
Ed.  Kleiner,  of  Zurich,  in  1886.  Molten  cryolite  was  decom- 
posed by  two  carbon  poles,  the  heat  generated  by  the  current 
first  melting  the  cryolite  and  then  electrolyzing  it.  Since  the 
motive  power  in  this,  as  in  all  electric  processes,  composes  one 
of  the  chief  elements  for  carrying  on  the  reduction,  the  Kleiner 
Gesellschaft,  formed  to  work  this  method,  made  an  attempt  to 
obtain  water  rights  at  the  falls  of  the  Rhine,  at  Schaffhauseni 
which  would  furnish  15,000  horse-power.  This  proposition 
being  refused  by  the  government,  an  experimental  plant  was 
started  at  the  Hope  Mills,  Tyddesley,  Lancashire,  England. 
The  results  were  not  encouraging  enough  to  allow  of  commer- 
cial success,  and  the  process  was  abandoned. 

An  electrolytic  method,  different  in  principle  from  both  the 
preceding,  is  the  invention  of  Mr.  Chas.  M.  Hall,  of  Oberlin, 
Ohio,  which  was  patented  in  the  United  States  in  April,  1889, 
but  applied  for  in  1886.  The  principle  involved  is  the  electric 
decomposition  of  alumina,  dissolved  in  a  fused  bath  of  the 
fluorides  of  aluminium  and  other  bases,  the  current  reducing 
the  dissolved  alumina  without  affecting  the  solvent.  This 
method  is  essentially  different  from  any  of  the  previous  elec- 
trical processes,  which  contemplated  and  operated  simply  the 
decomposition  of  a  molten  aluminium  salt,  such,  for  instance,  as 
the  solvent  used  by  Mr.  Hall.  The  knowledge  that  the  fused 
fluorides  dissolve  large  quantities  of  alumina,  and  that  the  elec- 
tric current  will  act  on  this  dissolved  alumina  without  decom- 


posing  the  solvent,  was  the  essence  of  Hall's  invention,  and  the 
source  of  another  revolution  in  the  aluminium  industry.  The 
process  has  been  operated  by  the  Pittsburgh  Reduction  Com- 
pany, from  1889  to  1891,  in  Pittsburgh,  Pa.,  since  1891  at  New 
Kensington,  Pa.,  on  the  banks  of  the  Allegheny  river,  eighteen 
miles  above  Pittsburgh.  During  1889  this  company  produced 
about  75  pounds  of  aluminium  a  day,  which  they  sold  at  $4.50 
per  pound ;  in  1 890  their  capacity  was  increased  to  400  poun'ds 
per  day,  and  the  selling  price  reduced  to  $2.00  per  pound; 
since  1892  the  works  ha,ve  been  again  enlarged  to  a  capacity  of 
nearly  one  ton  per  day,  and  the  selling  price  has  tended  stead- 
ily downwards  until  it  is  at  present  $0.50  per  pound.  During 
189s  this  company  expects  to  put  into  operation  a  very  large 
new  plant  at  Niagara  Falls,  using  power  generated  by  the  new 
tunnel.  This  works  will  utilize  up  to  6,000  horse-power,  and 
will  have  a  capacity  when  in  full  operation  of  6,000  to  8,000 
pounds  per  day.  This  improvement  will  place  the  United 
States  in  the  front  as  the  largest  aluminium-producing  country 
in  the  world. 

In  France,  Adolphe  Minet,  a  well-known  electrician,  experi- 
mented during  1887  and  1888  on  the  electrolysis  of  a  molten 
bath  containing  aluminium  fluoride  and  sodium  chloride,  fed 
by  the  addition  of  alumina  and  aluminium  fluoride.  From 
1888  to  1 89 1  this  process  was  run  on  an  experimental  scale 
at  the  works  of  Bernard  Bros.,  at  Creil,  making  about  35  pounds  * 
of  aluminium  per  day.  In  1890  a  larger  plant  was  put  up,  run 
by  water  power,  at  Saint  Michel,  Savoy,  having  a  much  larger 
capacity,  which  it  is  stated  had  been  increased  in  1894  to 
1,000  pounds  per  day.  In  1895,  this  plant  has  been  acquired 
by  a  French  company  who  will  operate  by  the  Hall  process. 

While  the  electrolytic  processes  so  far  considered  use  a  fluid 
bath,  and  operate  at  moderate  temperatures  with  a  current  of 
moderate  intensity,  there  have  been  devised  two  other  promi- 
nent processes  which  operate  in  a  somewhat  different  manner 
and  attain  to  economical  results.  These  primarily  depend  on 
the  enormous  temperature  attainable  by  the  use  of  a  powerful 


electric  arc,  and  secondarily  on  the  reduction  of  alumina  (which 
at  the  temperature  attained  becomes  fluid)  either  by  the  reduc- 
ing action  of  the  carbon  present  or  by  simple  electric  decompo- 
sition. Which  of  these  two  agencies  performs  the  reduction,  in 
either  process,  is  still  an  unsettled  question,  which  we  will  dis- 
cuss later  on. 

Before  going  further  with  the  history  of  these  two  processes, 
Cowles'  and  Heroult's,  it  may  not  be  inappropriate  to  take  note 
of  a  few  facts  antecedent  to  their  appearance.  It  is  well  known 
that  Sir  W.  Siemens  devised  an  electric  furnace  in  which  the 
heat  of  the  arc  was  utilized  for  melting  steel.  In  1882  Mr. 
Ludwig  Grabau,  in  Hanover,  Germany,  purchased  a  Siemens 
furnace  for  the  express  purpose  of  attempting  the  reduction  of 
alumina,  and  after  experimenting  successfully  for  some  time, 
modified  the  apparatus  so  as  to  work  it  continuously,  and  there- 
with made  aluminium  alloys ;  but  on  account  of  the  difficulties 
of  the  process,  and  the  impurity  of  the  alloys  produced,  Mr. 
Grabau  gave  up  the  experiments,  having  come  to  the  conclu- 
sion that  aluminium  alloys  to  be  technically  valuable  should  be 
obtained  in  a  state  of  almost  chemical  purity.  In  the  beginning 
of  1885  Dr.  Mierzinski,  in  his  book  on  aluminium,  presented 
some  very  striking  remarks  on  the  use  of  the  electric  furnace, 
which  are  so  much  to  the  point  that  they  are  well  worth  quoting 
in  this  connection :  "  The  application  of  electricity  for  produc- 
ing metals  possesses  the  advantage  not  to  be  ignored  that  a  de- 
gree of  heat  may  be  attained  with  it  such  as  cannot  be  reached 
by  a  blowpipe  or  regenerative  gas-furnace.  The  highest  furnace 
temperature  attainable  is  2500  to  2800°  C.,  but  long  before  this 
point  is  reached  the  combustion  becomes  so  languid  that  the 
loss  of  head  by  radiation  almost  equals  the  production  of  heat 
by  combustion,  and  hinders  a  further  elevation  of  temperature. 
But  in  applying  electricity  the  degree  of  heat  attainable  is  theo- 
retically unlimited.  A  further  advantage  is  that  the  smelting 
takes  place  in  a  perfectly  neutral  atmosphere,  the  whole  opera- 
tion going  on  without  much  preparation,  and  under  the  eyes  of 
the    operator.     Finally,   in    ordinary   furnaces,   the    refractory 


material  of  the  vessel  must  stand  a  higher  heat  than  the  sub- 
stance in  it,  whereas  by  smelting  in  an  electric  furnace  the 
material  to  be  fused  has  a  higher  temperature  than  the  crucible 
itself.  Since  the  attempt  to  produce  aluminium  by  the  direct 
reduction  of  alumina  by  carbon  is  considered  by  metallurgists 
as  impossible,  because  the  temperature  requisite  is  not  attain- 
able, the  use  of  the  electric  current  for  attaining  this  end  seems 
to  be  of  so  much  the  more  importance." 

The  Cowles  invention  was  patented  August  i8,  1885,  and 
was  first  publicly  described  before  the  American  Association 
for  the  Advancement  of  Science,  at  their  Ann  Arbor  meeting, 
August  28,  1885.  The  process  is  due  to  two  Cleveland  gen- 
tlemen, E.  H.  and  A.  H.  Cowles,  who  in  the  development  of 
their  process  associated  with  them  Prof.  Charles  F.  Mabery,  of 
the  Case  School  of  Applied  Science,  Cleveland,  as  consulting 
chemist.  The  Cowles  Electric  Smelting  and  Aluminium  Com- 
pany, formed  to  work  the  process,  erected  a  plant  at  Lockport, 
N.  Y.,  where  a  water  power  of  1200  horse-power  was  secured, 
and  where,  among  other  novel  apparatus,  the  largest  dynamo 
in  the  world,  made  especially  for  this  purpose  by  the  Brush 
Electric  Company,  was  in  operation.  Following  the  success  of 
this  plant  in  America,  the  Cowles  Syndicate  Company,  organ- 
ized to  work  the  patents  in  England,  put  in  operation  works  at 
Stoke-on-Trent  which  had  a  capacity  of  something  like  300 
lbs.  of  alloyed  aluminium  daily.  Springing  also  from  the 
Cowles  process  is  the  "Aluminium  Brass  and  Bronze  Com- 
pany," of  Bridgeport,  Conn.,  which  was  organized  in  July, 
1887,  and  controls  the  exclusive  rights  under  the  Cowles 
American  patents  of  manufacturing  the  alloys  of  aluminium 
into  sheet,  rods,  and  wire.  The  extensive  plant  of  this  com- 
pany employs  300  men,  and  has  been  erected  at  a  cost  of  nearly 

The  principle  made  use  of  in  the  Cowles  process  is,  briefly, 
that  a  powerful  electric  current  is  interrupted,  the  terminals 
being  large  carbon  rods,  and  the  space  between  having  been 
filled  with  a  mixture  of  alumina,  carbon,  and  the  metal  to  be 


alloyed,  the  intense  heat  generated  in  contact  with  this  mixture 
causes  the  metal  to  melt  and  the  alumina  to  be  reduced  to  alu- 
minium, which  combines  with  the  metal,  while  the  oxygen 
escapes  as  carbonic  oxide. 

It  is  interesting  to  note  as  separating  the  Cowles,  as  well  as 
the  Heroult,  process  from  the  previously-mentioned  electrolytic 
methods,  that  while  the  latter  produce  almost  exclusively  pure 
aluminium  in  their  electric  operation,  finding  it  inexpedient,  if 
not  perhaps  impossible,  to  add  other  metals  and  form  alloys  at 
once — the  former  experience  almost  the  reverse  of  these  condi- 
tions, and  as  yet  are  confined  exclusively  to  the  direct  produc- 
tion of  the  alloys. 

The  Heroult  process  was  first  put  in  practical  operation  on 
July  30th,  1888,  at  the  works  of  the  Swiss  Metallurgic  Com- 
pany (Societe  Metallurgique  Suisse),  at  Neuhausen,  near 
Schaffhausen.  The  patents  for  the  process  were  granted  in 
France  and  England  in  April  and  May,  1887,  and  in  the  United 
States  in  August,  1888.  The  company  named  above  is  com- 
posed of  some  of  the  largest  metal-workers  in  Switzerland. 
Previously  to  their  adoption  of  this  process  they  had  experi- 
mented with  Dr.  Kleiner's  electrolytic  method,  but  abandoned 
it,  and  on  becoming  the  owners  of  the  Heroult  process  imme 
diately  started  it  up  practically  on  a  large  scale,  and  with  signal 

The  process  consists  in  electrolyzing  molten  alumina  which 
has  been  rendered  fluid  by  the  heat  of  the  arc,  using  as  the 
positive  anode  a  large  prism  of  hard  carbon  and  as  the  negative 
a  substratum  of  molten  copper  or  iron,  the  arrangement  of  the 
parts  being  such  that  the  process  seems  to  proceed,  when  once 
well  under  way,  in  all  respects  as  tlfe  simple  electrolysis  of  a 
liquid.  Using  water  power  for  driving  the  dynamos,  the 
economical  production  of  alloyed  aluminium  at  4.5  francs  per 
kilo  (50  cents  per  pound),  was  an  assured  fact. 

The  success  of  this  process  at  Neuhausen  was  so  marked  as 
to  attract  general  attention,  and  in  the  latter  months  of  1 888 
several  large  German  corporations,  prominent  among  which  was 


the  Allgemeine  Electricitats  Gesellschaft  of  Berlin,  sent  repre- 
sentatives to  arrange  for  the  purchase  of  the  Heroult  patents 
for  Germany.  The  outcome  of  these  examinations  and  negotia- 
tions was  the  purchase  by  this  German  Syndicate  of  HerouU's 
continental  patents  and  the  founding  by  them  and  the  former 
Swiss  owners  of  the  Aluminium  Industrie  Actien-Gesellschaft, 
with  a  capital  of  10,000,000  francs.  In  December,  1888,  the 
new  company  took  possession  at  Neuhausen,  and  commenced 
the  construction  of  a  plant  many  times  larger  than  the  original 
one,  their  plans  also  including  the  erection  of  foundries  and 
mills  for  casting  and  manufacturing  their  alloys.  Dr.  Kiliani, 
the  well-known  writer  on  electro-metallurgical  subjects,  was 
working  manager  for  the  company.*  The  new  plant  utilized 
3000  horse  power,  and  had  a  capacity  of  3000  pounds  of  alloyed 
aluminium  daily. 

In  the  same  year,  the  Societe  Electro-Metallurgique  Fran- 
caise  established  a  works  at  Froges  (Isere)  12  miles  from 
Grenoble,  to  work  the  Heroult  process,  with  Kiliani's  modifica- 
tions. They  used  400  horse-power,  which  later  was  enlarged 
to  800,  and  in  1894  acquired  a  large  water  power  at  La  Praz, 
near  Modane,  where  works  have  been  erected  and  lately  put 
into  operation. 

The  process  now  used  here  and  in  Switzerland  is  not  the 
original  Heroult  process  as  previously  described.  Dr.  Kiliani 
introduced  some  modifications  in  the  apparatus,  but  no  pure ' 
aluminum  was  made  by  either  of  the  Heroult  works  until  the 
end  of  1889,  when  there  was  begun  the  use  of  cryolite  in  the 
furnace  to  reduce  the  melting  point  of  the  alumina  and  the 
electrical  tension  required  to  operate  it.  As  thus  modified,  the 
process  is  essentially  identical  in  principle  with  Hall's  process ; 
in  fact,  the  U.  S.  Patent  office  refused  Heroult's  application  for 
a  patent  on  account  of  Hall's  priority  to  the  process.  An  at- 
tempt was  made  in  1889  to  work  the  Heroult  alloy  process  in 
the   United    States,    an   experimental    plant   being   started   at 

*  Dr.  Kiliani  died  suddenly  in  January,  1895,  in  the  midst  of  his  duties. 


Bridgeport,  Conn.,  in  August  of  that  year,  but  it  was  stopped 
by  the  burning  out  of  the  dynamo.  In  1890  another  dynamo 
arrived  from  the  Oerlikon  works,  at  Zurich,  and  the  process 
was  operated  for  some  time  on  an  experimental  scale  at  Boon- 
ton,  N.  J.,  but  was  abandoned  in  1891. 

During  the  years  1885  to  1890  both  the  Cowles  and  Heroult 
alloy  processes  were  successful  in  producing  aluminium  in  al- 
loys at  a  lower  cost  than  the  market  price  of  pure  aluminium, 
and  therefore  built  up  a  considerable  business.  Since  pure 
aluminium  has  reached  so  low  a  price,  metal  mixers  prefer  to 
make  their  own  alloys  from  the  pure  metal,  and  the  ready-made 
alloys  have  lost  their  market. 

The  Alliance  Aluminium  Company  of  London,  England,  was 
organized  in  the  early  part  of  1888,  with  a  nominal  capital  of 
^500,000.  This  company  owned  the  English,  German,  French, 
and  Belgian  patents  of  Prof.  Netto,  of  Dresden,  for  the  manu- 
facture of  sodium  and  potassium  and  the  reduction  of  cryolite 
thereby ;  the  patents  of  Mr.  Cunningham  for  methods  of  reduc- 
tion of  the  same  metals ;  and  methods  devised  by  Prof.  Netto 
and  Dr.  Saloman,  of  Essen,  for  producing  aluminium  of  great 
purity  on  a  commercial  scale.  The  two  latter  named  gentle- 
men are  said  to  have  invented  their  processes  after  long  ex- 
perimenting at  Krupp's  works  at  Essen;  and,  since  the  ap- 
paratus used  was  mounted  on  trunnions,  many  rumors  were 
spread  by  the  newspapers  that  aluminum  was  being  made  (by 
tons,  of  course)  in  a  Bessemer  converter  by  Krupp,  of  Essen. 
Prof.  Netto  reduced  sodium  by  a  continuous  process,  by  allow- 
ing fused  caustic  soda  to  trickle  over  incandescent  charcoal  in  a 
vertical  retort,  the  apparatus  containing  many  ingenious  details 
and  giving  promise  of  being  quite  economical.  One  method  of 
using  the  sodium  in  reduction  consisted  in  the  use  of  a  plunger 
to  which  bars  of  sodium  were  attached  and  held  at  the  bottom 
of  a  crucible  full  of  molten  cryolite ;  another  depended  on  the 
use  of  a  revolving  cylinder  in  which  the  cryolite  and  sodium 
reacted,  and  appears  more  chimerical  than  Netto's  other  pro- 
positions. This  latter  device,  however,  is  said  to  have  been 
operated  at  Essen. 


In  June,  1888,  the  Alliance  Company  were  located  at  King's 
Head  Yard,  London,  E.  C,  and  several  small  reduction  furnaces 
were  being  operated,  each  producing  about  50  lbs.  of  alumin- 
ium a  day,  estimates  of  the  cost  at  which  it  was  made  giving 
6  to  8  shillings  per  pound.  In  the  early  part  of  1889  the 
"  Alkali  Reduction  Syndicate,  Limited,"  leased  ground  at  Hep- 
burn on  which  to  erect  works  for  making  sodium  by  Cunning- 
ham's patents,  the  sodium  produced  being  sent  to  Wallsend, 
near  Newcastle-on-Tyne,  where  the  Alliance  Company's  reduc- 
tion works  were  located. 

In  1890  this  company  could  not  profitably  compete  with  the 
electrolytic  processes,  and  in  1 892  their  works  were  sold  at  auc- 

Ludwig  Grabau,  of  Hanover,  Germany,  has  made  several 
patented  improvements  in  producing  aluminium,  which  are  in 
the  same  direction  as  Prof.  Netto's  methods.  Mr.  Grabau  be- 
lieves that  in  order  that  aluminium  may  possess  its  most  valuable 
qualities,  either  for  use  alone  or  in  alloying,  it  should  be  of 
almost  chemical  purity,  and  as  the  best  means  of  attaining  this 
end  economically  he  has  improved  the  sodium  method  on 
these  three  lines  : — 

1st.   Production  of  cheap  pure  aluminium  fluoride. 

2d.   Production  of  cheap  sodium. 

3d.  Reduction  in  such  a  manner  that  no  possible  impurities 
can  enter  the  reduced  metal,  and  that  the  sodium  is  completely 

Mr.  Grabau  has  devised  processes  for  making  pure  alumin- 
ium fluoride  from  kaolin,  sodium  by  electrolysis  of  fused  salt, 
and  has  succeeded  in  producing  some  very  pure  aluminium, 
but  not  cheaply  enough  to  compete  with  the  Hall  and  Heroult 

Col.  William  Frishmuth,  of  Philadelphia,  operated  a  small 
chemical  works,  and  before  i860  made  sodium  by  Deville's 
process,  and  with  it  made  aluminium  in  small  quantities.  He 
claimed  to  have  other  methods  of  producing  aluminium  cheaply, 
but  none  of  them  were  practicable.     He  deserves  credit  for  hav- 


ing  made  a  good  casting  of  the  aluminium  tip  on  tlie  Wasiiing- 
ing  Monument  at  our  national  capital. 

In  1889  the  aluminium  industry  was  finely  represented  at  the 
Paris  Exposition.  It  was  the  period  in  which  the  sodium  pro- 
cesses were  at  their  culmination,  and  the  electrical  processes 
just  becoming  serious  competitors.  A  detailed  account  of  the 
exhibits  reads  as  follows : 

Societe  Anonyme  pour  I'lndustrie  de  1' Aluminium :  In  a 
large  case,  the  frame  of  which  was  aluminium  bronze,  samples 
of  aluminium,  ferro-aluminium,  aluminium  bronze,  forged  and 
rolled,  and  numerous  articles  of  the  latter  alloy.  Cowles  Elec- 
tric Smelting  and  Aluminium  Company :  Samples  of  ferro-alu- 
uminium,  aluminium  bronze  and  aluminium  brass  of  various 
grades,  aluminium  silver,  and  numerous  useful  articles  made  of 
these  alloys.  Brin  Bros. :  Samples  of  aluminium  with  thin  iron 
and  steel  castings  made  by  its  use.  The  Alliance  Aluminium 
Company:.  Two  large  blocks  of  aluminium,  cast  hollow,  weigh- 
ing possibly  1,000  pounds  and  500  pounds,  respectively.  The 
inclosing  balustrade  and  decorations  were  principally  of  alu- 
minium or  aluminium  bronze.  The  Aluminium  Company, 
Limited  :  A  solid  casting  of  aluminium  bronze  weighing  y^  ton, 
and  on  this  a  solid  block  of  98  per  cent,  aluminium  weighing 
the  same.  In  the  corners  of  the  case  piles  of  ingots  of  99  per 
cent,  aluminium,  10  per  cent,  bronze,  5  per  cent,  bronze,  10 
per  cent,  ferro-aluminium,  and  20  per  cent,  aluminium  steel. 
Besides  which  were  a  7-inch  bell,  springs,  statues,  aluminium 
plate,  round  and  square  tubes,  wire,  sheet,  etc.  Such  were  the 
aluminium  exhibits,  which  attracted  as  much  interest  as  the 
historic  ingot  of  1855  did  at  its  debut,  and,  not  taking  into  ac- 
count that  Mr.  Hall's  process  was  not  represented  and  that  the 
German  makers  were  debarred  from  exhibiting  because  of  in- 
ternational pique,  yet  the  exhibit  shown  was  one  which  demon- 
strated the  great  advances  made  in  the  previous  five  years. 

Since  1 890,  the  progress  of  the  aluminium  industry  has  been 
steady  but  sure.  The  sodium  processes  have  dropped  alto- 
gether from  the  race,  and  the  electrical  processes  occupy  the 


field.  Among  these,  the  processes  producing  alloys  only  have 
dropped  out  of  sight.  Among  those  that  remain,  only  those 
favorably  situated,  near  abundant  water  power  and  with  cheap 
supplies  of  alumina,  have  flourished.  The  industry  has  reached 
a  strict  commercial  basis,  in  which  every  cent  of  cost  has  to  be 
considered,  and  every  item  of  expense  reduced  to  a  minimum. 

In  1890  the  Cowles  Electric  Smelting  and  Aluminium  Com- 
pany began  selling  pure  aluminium.  They  were  sued  by  the 
Pittsburgh  Reduction  Company  for  infringement  of  the  Hall 
patents,  and  in  the  early  part  of  1893  were  enjoined  by  the 
courts  from  continuing  their  pure-metal  process,  it  being  de- 
clared an  infringement  of  Hall's  patents. 

Mention  should  be  made  of  the  aluminium  exhibit  at  the 
Columbian  Exposition  in  Chicago,  1893.  The  only  makers 
represented  were  the  Pittsburgh  Reduction  Company,  but  their 
exhibit  was  a  very  satisfactory  representation  of  the  state  of  the 
art.  A  working  model  of  an  extraction  pot  was  shown,  hun- 
dreds of  pounds  of  the  metal  in  all  shapes  and  worked  in  every 
way,  a  fine  set  of  aluminium  alloys,  and  several  cases  of  manu- 
factured goods  made  from  their  metal  by  various  American 
firms.  Mr.  Hirsh  of  Chicago  showed  aluminium  electroplated 
on  other  metals  and  on  wood.  The  writer  exhibited  a  metal- 
lurgical suite  showing  the  minerals  from  which  aluminium  is 
extracted,  samples  of  aluminium  made  by  the  various  processes 
which  have  been  used,  samples  showing  the  physical  properties 
of  the  metal,  its  working,  soldering,  etc.,  and  a  large  number  of 
its  alloys. 

The  statistics  about  to  be  given  will  show  graphically  the 
story  of  the  rise  of  the  aluminium  industry.  The  last  ten  years 
have  witnessed  an  undreamt-of  progress.  Hereafter  the  lower- 
ing in  price  can  only  be  counted  at  a  few  cents  a  pound,  but 
the  increase  of  production  may  be  noted  in  thousands  of  tons. 
A  most  fitting  ending  to  this  historical  sketch  would  be  simply 
to  repeat  what  I  wrote  three  years  ago,  viz.,  "  The  nineteenth 
century  will  live  in  history  as  that  century  which  gave  to  the 
world  the  railway,  the  telegraph,  the  telephone,  the  dynamo, 
Bessemer  steel  and  aluminium." 



The  following  table  shows  the  price  at  which  aluminium  has 
been  sold  since  it  was  first  placed  on  the  market : 

Dale.  Place.  Per  kilo.  Per  pound. 

1856  (Spring)    Paris looo  fr.  ^90.90 

1856  (August)       "      300  "  27.27 

1859                       "      200"  17-27 

1862                       "      130"  11.75 

1862                    Newcastle ii-75 

1878                    Paris 130"  11.75 

1886  "      12.00 

1887  Bremen 8.00 

1888  London 4.84 

1889  Pittsburgh 2.00 

1891  "  1 1.50 

1892  "  i.oo 

1893  "  0-75 

1894  "  0.50 

1895  Switzerland 3  M.  0.35 

Until  1885  the  selling  price  of  aluminium  bronze  depended 
directly  on  the  price  of  aluminium,  being  about  $1.50  per 
pound  for  the  ten'  per  cent,  alloy.  With  the  advent  of  the 
Cowles  and,  later,  the  Heroult  alloy-processes,  the  price  fell 
below  what  the  contained  aluminium  would  have  cost,  as  is 
shown  by  the  selling  price  of  the  ten  per  cent,  bronze,  as  fol- 

Date.  Place.                                                               Per  kilo.  Per  pound. 

1878             Paris 18.00  fr.  gi.64 

1885            Cowles  Bros 4.50  "  0.40 

1888                 "          "      3-85  "  0.35 

1888            Heroult  process,  Neuhausen 3.30  "  0.30 

Since  1889  the  cost  of  the  bronze  has  again  been  dependent 
on  the  cost  of  the  pure  metal,  so  that  no  separate  figures  are 
necessary,  With  copper  at  $0.10  per  pound,  and  aluminium 
at  $0.50,  the  cost  of  10  per  cent,  bronze  is  not  over  $0.20  per 

As  to  the  amount  of  aluminium  which  has  been  produced. 


we  can   make  the  following  estimates,  gleaned  from  various 
sources : 



1854-56  Deville 25 

1859  Nanterre  (Deville) 720 

1859  Rouen  (Tissier  Bros.) 960 

1865  France 1,090 

1869                      "        455 

1872  Sallndres  (H.  Merle  &  Co.)  1,800 

1882                       "               "             "          2,350 

1884                       "               "             "          2,400 

1887  France  3,500 

1888  "  4,500 

1889  "  14,840 

1890  "  37,°oo 

1891  "  36,000 

1892  "  40,000 

A  careful  estimate  of  the  total  amount  made  in  France  by 
the  Deville  process,  from  1855  to  1888,  places  it  at  43,000 
kilos.  Since  1888,  there  has  been  made  by  other  processes 
128,000  kilos  up  to  the  year  1893,  making  a  total  of  171,000 
kilos,  or  375,000  pounds. 



1872  Bell  Bros 1,650 

1889  Castner  process 50,000 

1891  Electrolytic  processes 90,000 

1892  "  "         90,000 

The  total  English  production  up  to  1890  was  probably  not 
over  70,000  pounds.  The  Castner  process  produced  altogether 
from  July,  1888  to  1891,  250,000  pounds.  The  total  produced 
in  England  to  the  end  of  1 892  is  therefore  in  the  neighborhood 
of  450,000  pounds. 



1890  Neuhausen 40,540 

1891  "  168,670 

1892  "  300,000 

1893  "  480,000 

1894  •'  600,000 


The  total  production  of  these  works  to  the  end  of  1894  was 
over  1,500,000  kilos,  or  3,300,000  pounds. 

United  States. 


1883  Frishmuth 70 

1884  "         125 

1885  "         230 

1885            Cowles  Bros,  (in  alloys) 450 

'886                       "               "             6,500 

•887                       "               "             17,800 

1888  Pure  and  alloyed 19,000 

1889  "  47,468 

1890  "  61,281 

1891  "  150,000 

1892  "  259,885 

1893  "  • 333,629 

1894  '•  706,000 

World's  Production  to  End  of  1892. 

Kilos.  Pounds. 

France 171,000  376,000 

England 204,500  450,000 

Switzerland 500,000  1,100,000 

Germany  (1885- 1 889) 50,000  110,000 

United  States 250,000  550,000 

Total 1,175,500  2,586,000 

The  amount  made  in  1 893  was  as  follows : 

France  (estimated) 40,000  kilos. 

Switzerland 480,000    " 

United  States 150,000    " 

Total 670,000    "  =:  1,474,000  pounds. 

An  estimate  for  1 894  would  be  as  follows : 

France 100,000  kilos. 

Switzerland 600,000    " 

United  States 320,000    " 

Total 1,020,000    "  =  2,244,000  pounds. 

The  total  amount  of  aluminium  made  from  1855  to  the  be- 


ginning  of  1895  is,  therefore,  in  the  neighborhood  of  2,865,500 
kilos,  or  6,304,000  pounds,  while  the  annual  production  has 
reached  1,000  long  tons,  and  will  probably  be  increased  during 
1895  to  nearly  2,000  tons. 

In  comparing  these  figures  with  the  production  of  other 
metals,  it  is  important  to  bear  in  mind  the  low  specific  gravity 
of  aluminium.  For  most  practical  applications,  the  bulk  of  the 
metal  used  is  a  fixed  quantity,  and  1,000  tons  of  aluminium 
are  equal  in  volume  to 

4,600  tons  of  lead. 
4,000     "      "  silver. 
3,500    "     "  nickel. 
3,300    "     "  copper. 
2,800    "     "  tin. 
2,700     "      "  zinc. 



There  is  no  other  useful  metal,  iron  not  excepted,  which 
is  so  widely  scattered  over  the  earth  and  occurs  in  such 
abundance.  F.  W.  Clarke  of  the  Smithsonian  Institution  has 
calculated  that  the  percentage  of  aluminium  in  the  earth's  crust, 
as  far  as  it  is  known  to  us,  is  7.81,  while  that  of  iron,  the  next 
most  abundant  element,  is  5.46. 

Aluminium  is  not  found  metallic.  Stocker  *  made  the  state- 
ment that  aluminium  occurred  as  shining  scales  in  an  alumina 
formation  at  St.  Austel,  near  Cornwall,  but  he  was  in  error. 
But  the  combinations  of  aluminium  with  oxygen,  the  alkalies, 
fluorine,  silicon,  and  the  acids,  etc.,  are  so  numerous  and  occur 
so  abundantly  as  not  only  to  form  mountain  masses,  but  to  be 
also  the  bases  of  soils  and  clays.  Especially  numerous  are  the 
combinations  with  silicon  and  other  bases,  which,  in  the  form 
of  feldspar  and  mica,  mixed  with  quartz,  form  granite. 

These  combinations,  by  the  influence  of  the  atmospheric  air 
and  water,  are  decomposed,  the  alkali  is  replaced  or  carried 
away,  and  the  residues  form  clays.  The  clays  form  soils,  and 
thus  the  surface  of  the  earth  becomes  porous  to  water  and 
fruitful.  It  is  a  curious  fact  that  aluminium  is  rarely  found  in 
animals  or  plants.  According  to  Church, f  alumina  is  found 
only  in  a  few  vascular  cryptogamous  plants,  whose  ash  con- 
tains up  to  20  per  cent. 

Ricciardi  concluded  from  numerous  experiments  that  the 
assimilation  of  alumina  by  plants  does  not  depend  upon  the 
abundance  of  alumina  in  the  soil,  and  that,  generally  speaking, 

*  Joum.  fr.  prakt.  Chem.,  66, 470. 

t  Proc.  Royal  Society,  Vol.  44,  p.  121. 



there  is  more  found  in  the  trunk  and  branches,  less   in  the 
husks  and  seeds,  and  least  in  the  leaves. 

Most  of  the  aluminium  compounds  appear  dull  and  disagree- 
able, such  as  feldspar,  mica,  pigments,  gneiss,  amphibole,  por- 
phyry, eurite,  trachyte,  etc. ;  yet  there  are  others  possessing 
extraordinary  lustre,  and  so  beautiful  as  to  be  classed  as  prec- 
ious stones.     Some  of  these,  with  their  formulae,  are : 

Ruby AI2O3 

Sapphire Al^Oj 

Garnet (Ca.Mg.Fe.Mn)3Al2Si30,2 

Cyanite AUSiOj 

Some  other  compounds  occurring  frequently  are : 

Turquoise AljPPs.HjAljOs.aHjO 

Lazulite (MgFe)AljP203  -|-  Aq 

Wavellite 2AI2P2O8.H1.AI2O6.9H2O 

Topaz 5AL,Si05.Al,SiFi„ 

Cryolite Al^Fg.eNaF 

Diaspore AIJO3.H2O 

Bauxite   AI2O3.2H2O 

Aluminite AlaSOe.gH^O 

Alunite K^s6i.Al^Sfi,^.2H^Alfii 

Soda  Feldspar NajAl2Si60ig 

Potash  Feldspar KjAljSigOjj 

Lime  Feldspar CaAljSijOg 

Kaolin Al2SijO,.2H20 

Bauxite  and  cryolite  are  the  minerals  most  used  for  produc- 
ing aluminium,  and  their  preference  lies  mainly  in  their  purity. 
Native  alums  generally  occur  in  out  of-the-way  places  and  not 
in  beds  of  very  large  extent. 


Bauxite  is  a  hydrous  aluminium  oxide  of  variable  composi- 
tion, sometimes  approaching  diaspore  in  its  proportion  of  water, 
but  with  the  aluminium  always  more  or  less  replaced  by  iron, 
and  some  silica  disseminated  through  it.  Its  color  is  creamy 
white  when  free  from  iron,  and  its  structure  usually  pisolitic, 
that  is,   in  small    globules   like  peas.     It  was   first   found    in 


France,  near  the  town  of  Baux,  large  deposits  occurring  in 
the  departments  of  Var  and  Bouches  du  Rhon,  extending  from 
Tarascon  to  Antibes.  Several  of  these  beds  are  a  dozen  yards 
thick,  and  sixteen  kilometers  in  length.  Deposits  are  also 
found  in  the  departments  of  I'Herault  and  I'Arriege.  Very  im- 
portant beds  are  found  in  Styria,  at  Wochein,  and  at  Freis- 
stritz,  in  Austria,  a  newly  discovered  locality  where  the  mineral 
is  called  Wocheinite.  Here  it  has  a  dense,  earthy  structure, 
while  that  of  France  is  conglomerate  or  oolitic.  Deposits 
similar  to  those  of  France  are  found  in  Ireland  at  Irish  Hill, 
Straid,  and  Glenravel.  Further  deposits  are  found  in  Hadamar 
in  Hesse,  at  Klein  Steinheim,  Langsdorff,  and  in  French 

In  the  United  States  large  beds  have  been  found  in  Alabama, 
Georgia,  and  Arkansas.  Those  of  Georgia  have  been  worked 
since  1890,  and  are  now  affording  a  large  part  of  all  the 
bauxite  consumed  in  this  country.  The  deposits  of  the  Coosa 
Valley  in  Georgia  and  Alabama  are  worked  by  three  com- 
panies, the  Republic  Mining  and  Manufacturing  Company,  the 
Georgia  Bauxite  and  Mining  Company,  and  the  Southern 
Bauxite  Mining  and  Manufacturing  Company.  These  three 
companies  produced,  in  1893,9,200  tons,  which  was  three-fifths 
of  the  total  bauxite  consumed  in  the  United  States,  the  rest 
being  imported  from  Ireland.  The  ore  is  found  in  beds  or 
pockets,  and  while  the  quantity  in  sight  is  not  inexhaustible, 
yet  there  is  sufficient  for  many  years  to  come,  at  the  pres- 
ent rate  of  mining.  These  bauxites  are  as  pure  as  those 
of  Europe,  and  the  manufacturers  using  them  say  they  are 
more  easily  worked  and  so  prefer  them  to  the  imported,  even 
though  they  often  carry  less  alumina  and  cost  more.  The 
Arkansas  ore  occurs  in  tertiary  formations,  in  irregular  de- 
posits of  5  to  40  feet  in  thickness,  not  over  300  feet  above  tide 
water.  H.  L.  Fletcher,  of  Little  Rock,  owns  much  of  the  land 
on  which  they  occur. 

The  cost  of  imported  bauxite  is  $5  to  $7  a  ton ;   of  Ameri- 
can bauxite   $5  to   12  per  long  ton,  according  to  where  the 



market  is;  best  selected  Georgia  bauxite  brings  $io  per  ton 
in  New  York  city. 

The  following  are  analyses  of  foreign  bauxites ;  besides  the 
ingredients  given  there  are  also  traces  of  lime,  magnesia,  sul- 
phuric, phosphoric,  titanic  and  vanadic  acids. 

Alumina  ■  •  ■ 
Ferric  oxide 


Alkalies.  • . . 



























Alumina  ■  ■ . 
Ferric  oxide 


Alkalies  .  ■  - 

Alumina  •  •  • 
Ferric  oxide 














2.1 1 


















1 1.0 












6.4 1 





Index: — 

I  and  2.  From  Baux  (Deville). 

Dark  \ 

T  ■  vj  ]■  Wocheinite  (Drechsler). 

Red  brown  \ 

Yellow  >■  Bauxite  from  Freisstritz  (Schnitzer). 

White  > 

White  Wocheinite  (L.  Mayer  and  O.  Wagner). 

Bauxite  from  Irish  Hill. 



10.  Bauxite  from  Co.  Antrim  (Spruce). 

11.  «        "     Glenravel  (F.  Hodges). 

12  and  13.        "        "     Hadamar  in  Hesse  (Retzlaff). 

14.  From  Klein-Steinheim  (Bischof). 

15  and  16.  From  Langsdorfi  (I.  Lang). 

17.  Bauxite  from   Dublin,  Ireland,  brought   to  the   Laurel  Hill  Chemical 

Works,  Brooklyn,  L.  I.,  and  there  used  for  making  alums.  It  is  dirty 
white,  hard,  dense,  compact,  and  in  addition  to  the  ingredients  given 
above  contains  0.59  per  cent,  of  lime  and  some  titanic  acid.  It  costs 
$6  per  ton  laid  down  in  the  works.  The  above  analysis,  made  by  Mr. 
Joiiet,  is  furnished  me  by  the  kindness  of  the  superintendent  of  the 
works,  Mr.  Herreshoff. 

The  American  bauxites  are    fully  equal  to   the  foreign    in 
quality,  as  is  shown  by  the  following  analyses : 

Ferric  Oxide. 



Titanic  Acid. 


Alumina |      37-62 

























Alumina  — 
Ferric  Oxide 



Titanic  Acid 



















18.  Little  Rock  Region,  Pulaski  Co.,  Arkansas. 

jg  >I  «  "  "  " 

20.  Red  variety.  Saline  Co.,  Arkansas. 

21.  Pink       " 

22.  White  variety,  Floyd  Co.,  Georgia. 


24.  Georgia  Bauxite  Company. 
2c  "  "  " 

26.  Wharwhoop  Mine,  Cherokee  Co.,  Alabama. 

27.  Red  variety,  Cherokee  Co.,  Alabama. 


Regarding  French  bauxites,  Francis  Laur,  the  first  to  work 
the  French  deposits,  states*  that  one  of  their  peculiarities  is 
that  the  bulk  of  that  mined  contains  a  nearly  constant  amount 
of  alumina,  of  silica,  ferric  oxide  and  water  taken  together,  and 
of  other  impurities.     The  proportions  are  very  nearly 

Alumina 68  to  70  per  cent. 

Silica,  ferric  oxide  and  water 27         " 

Other  impurities 3  to  4         " 

In  the  bauxite  from  Baux,  that  first  worked,  the  silica,  ferric 
oxide  and  water  are  present  in  about  equal  proportions ;  that 
is,  about  8  to  10  per  cent,  of  each.  In  the  pale  bauxite  from 
Villeveyrac  (Herault)  there  is  almost  no  iron,  and  the  27  per 
cent,  is  nearly  evenly  divided  between  silica  and  water ;  what 
small  amount  of  ferric  oxide  does  occur  in  it  can  be  put  into 
the  list  of  "  other  impurities."  The  red  bauxite,  discovered  in 
1880  in  the  south  of  France,  is  very  constant  in  composition, 
and  may  be  regarded  as  the  inverse  of  the  pale  variety.  In  this 
red  kind  the  silica  is  so  small  as  to  be  relegated  to  the  acces- 
sory constituents,  while  water  and  ferric  oxide  alone  make  up 
the  27  per  cent.  These  three  varieties  represent  the  three  types 
of  bauxite  which  are  mined  in  large  quantities.  The  pale 
variety,  being  low  in  iron,  is  preferred  for  making  aluminium 
sulphate  by  treatment  with  sulphuric  acid,  which  attacks  it  very 
readily;  the  red  kind  is  preferred  for  the  sodium  carbonate 
treatment,  as  the  iron  does  not  interfere,  while  silica  is  kept  out 
of  the  alumina  produced.  Besides  these  kinds,  some  varieties 
are  found  with  the  27  per  cent,  either  all  water,  all  silica  or  all 
ferric  oxide.  We  would  thus  have,  as  the  composition  of  the 
typical  kinds  of  bauxite  found  in  France,  the  following: 

Water.  Silica.  Ferric  oxide. 

Hyaline  bauxite 27                 o  o 

Silicious  type,  compact o  27  o 

Ferruginous  type,  in  pisolites o                 o  27 

Red  bauxite  of  Var 131^             o  131^ 

Pale  bauxite  of  Villeveyrac 131^  i^}4  o 

Mixed  bauxite  of  Baux 9                9  9 

*  Trans.  Am.  Inst.  Mining  Eng.,  Feb.,  1894. 


Mr.  A.  E.  Hunt,  of  Pittsburgh,  in  the  discussion  of  this  paper, 
remarked  that  there  are  vast  quantities  of  bauxite  in  Georgia, 
Alabama  and  Arkansas,  which  run  low  in  both  silica  and  ferric 
oxide,  containing  less  than  5  per  cent,  of  both  these  ingredients, 
but  with  about  4.5  per  cent,  of  titanic  acid.  It  is  his  experience 
that  when  the  water  of  hydration  is  below  31  per  cent.,  in  the 
greyish  and  white  bauxite  from  Georgia  and  Alabama,  the 
silica  is  always  high.  If  the  bauxite  is  red,  however,  the  water 
may  be  low  without  the  silica  being  high.  He  cites  the  follow- 
ing analyses  illustrating  this  point : 

Combined  water. 


Ferric  oxide. 

Titanic  acid. 



























It  will  be  seen  that  Mr.  Laur's  generalizations  regarding 
French  bauxites  do  not  hold  good  for  the  American  varie- 
ties ;   the  constancy  of  the  titanic  aci,d  is  also  remarkable. 


Cryolite  was  first  found  at  Ivigtuk  in  Arksut-fiord,  west  coast 
of  Greenland,  where  it  constitutes  a  large  bed  or  vein  in  gneiss. 
It  was  very  rare  even  in  mineralogical  collections  until  1855, 
when  several  tons  were  carried  to  Copenhagen  and  sold  under 
the  name  of  "  soda  mineral."  It  is  a  semi-transparent,  snow- 
white  mineral.  When  impure  it  is  yellowish  or  reddish,  even 
sometimes  almost  black.  It  is  shining,  sp.  gr.  2.95,  and  hard- 
ness 2.5  to  3.  It  is  brittle,  not  infrequently  contains  ferrous 
carbonate,  sulphide  of  lead,  silica,  and  sometimes  columbite. 
It  is  fusible  in  the  flame  of  a  candle,  and  on  treatment  with 
sulphuric  acid  yields  hydrofluoric  acid.  As  will  be  seen  further 
on,  cryolite  was  first  used  by  the  soap-makers  for  its  soda ;  it 
is  still  used  for  making  soda  and  alumina  salts,  and  to  make  a 
white  glass  which  is  a  very  good  imitation  of  porcelain.  The 
Pennsylvania  Salt  Company  in   Philadelphia    import  it  from 


Ivigtuk  by  the  ship-load  for  these  purposes ;    lately  they  have 
discontinued  making  the  glass.     Cryolite  is  in  general  use  as  a 
flux.     A   very  complete  description  of  the  deposit   at  Ivigtuk 
can  be  found  in  Hoffman's  "  Chemische  Industrie." 
Pure  cryolite  contains 

Aluminium l3-° 

Fluorine 54-5 

Sodium 32.5 


Or  otherwise  stated, 

Aluminium  fluoride 40.25 

Sodium  fluoride ■* 59-75 


From  the  reports  in  the  Mineral  Resources  of  the  United 
States  we  find  that  there  was  imported  by  the  Pennsylvania 
Salt  Company  in  1892,  8000  long  tons,  which  was  valued  at 
$9  a  ton.  The  importers  say  this  value  is  too  low ;  they  sell 
what  they  call  pure  prepared  cryolite  at  $60  a  ton.  This  so 
called  pure  article  was  found  by  Prof.  Rogers,  of  Milwaukee,  to 
contain  two  per  cent,  of  silica  and  one  per  cent,  of  iron ;  in 
fact,  the  whitest  cryolite  always  contains  silica  microscopically 
disseminated  through  it,  which  cannot  be  separated  out  by  any 

The  only  known  deposit  of  cryolite  in  the  United  States  is 
that  found  near  Pike's  Peak,  Colorado,  and  described  by  W. 
Cross  and  W.  F.  Hillebrand  in  the  "American  Journal  of 
Science,"  October,  1883.  It  is  purely  of  mineralogical  import- 
ance and  interest,  occurring  in  small  masses  as  a  subordinate 
constituent  in  certain  quartz  and  feldspar  veins  in  a  country 
rock  of  coarse  reddish  granite.  In  composition,  however,  it  is 
practically  identical  with  the  Greenland  cryolite,  so  that  the 
following  analysis  by  Mr.  Hillebrand  will  stand  for  a  typical 
analysis  of  cryolite  as  found  in  nature : 


Fluorine 53.55  per  cent. 

Aluminium , 12,81        " 

Sodium 32.40        " 

Ferric  Oxide 0.40        " 

Lime 0.28        " 

Water 0.30        " 


Until  1869  the  sole  sources  of  corundum  were  a  few  river 
washings  in  India  and  elsewhere,  where  it  was  found  in  scat- 
tered crystals.  Its  cost  was  twelve  to  twenty-five  cents  a 
pound.  Within  the  last  twenty  years  numerous  mines  have 
been  opened  in  the  eastern  United  States,  the  first  discovery  of 
which  was  due  to  Mr.  W.  P.  Thompson,  and  is  thus  described 
by  him :  * 

"  In  1869,  in  riding  over  a  spur  of  the  Alleghenies  in  north- 
ern Georgia,  I  found  what  has  proven  to  be  an  almost  inex- 
haustible mine  of  corundum  in  the  chrysolite  serpentine,  the  first 
instance  on  record  of  the  mineral  being  found. /«  situ.  Previ- 
ously it  had  been  washed  out  of  debris  at  Cripp's  Hill,  N.  C, 
and  at  a  mine  in  West  Chester,  Pa.,  both  on  the  slopes  of  the 
chrysolite  serpentine.  The  clue  being  thus  obtained  accident- 
ally, about  thirty  mines  were  shortly  afterwards  discovered  in 
the  same  formation ;  but  of  the  thousands  of  tons  thus  far  dug 
out,  the  larger  portion  has  come  from  the  mines  I  discovered. 

"  At  present  it  can  be  bought  at  about  ten  dollars  per  ton  at 
the  mines.  It  is  nearly  pure  alumina.  Disapore,  a  hydrated 
alumina,  is  also  found  in  the  same  region  and  locality.  Corun- 
dum will  probably  always  be  the  principal  source  in  America 
of  material  from  which  to  manufacture  pure  aluminium ;  but  in 
Great  Britain,  in  all  probability,  manufacturers  must  look  to 
alumina  prepared  artificially  from  cryolite  or  from  sulphate  of 

In  1892  the  production  of  corundum  in  the  United  States 
was  somewhat  over  2000  short  tons,  valued  at  $40  a  ton  when 
sifted  and  broken  to  proper  sizes  for  the  market,  the  Hamp- 

*  Journal  of  the  Society  of  Chemical  Induustry,  April,  1886. 


den  Emery  Company,  at  Laurel  Creek,  Ga.,  and  at  Corundum 
Hill,  N.  C,  and  the  Unionville  Corundum  Mines  Company,  at 
Unionville,  Chester  Co.,  Pa.,  being  the  principal  producers. 
Thus,  while  corundum  may  be  worth  in  bulk  at  the  mines  only 
$io  a  ton,  yet  it  is  extremely  hard  to  crush,  and  when  broken 
up  fine  is  worth  far  more  as  an  abrasive  than  as  an  aluminium 
ore.  The  present  large  development  of  bauxite  mining  has 
completely  nullified  the  use  of  corundum  as  a  source  of  alumin- 
ium, and  I  do  not  suppose  that  at  present  a  single  pound  of 
aluminium  is  being  made  from  it. 


The  mineral  kaolin  is  variously  known  as  white  china  clay, 
fuller's- earth,  or  pure  white  clay.  It  is  essentially  a  hydrated 
silicate  of  aluminium,  containing  when  pure 

Alumina 39.8  per  cent. 

Silica 46.3 

Water 13.9        " 

Its  chemical  formula  is  Al2O3.2SiO2.2H2O.  If  the  water  is 
driven  off  by  calcination,  the  residue  contains  46.2  per  cent. 
of  alumina,  or  24.4  per  cent,  of  aluminium. 

Kaolin  has  been  formed  mostly  by  the  atmospheric  decom- 
position of  feldspar,  the  alkalies  of  which  are  changed  into 
carbonates  by  the  carbonic  acid  of  the  rain  water,  and  are  then 
leached  out,  carrying  with  them  part  of  the  silica  in  solution, 
and  leaving  kaolin,  according  to  the  reaction, 


Kaolin  acquires  a  certain  plasticity  when  mixed  with  water. 
Hydrochloric  and  nitric  acids  have  no  action  on  it,  but  cold 
sulphuric  acid  dissolves  its  alumina,  setting  the  silica  at  liberty. 
It  is  infusible  unless  contaminated  with  particles  of  feldspar  or 
calcium  sulphate,  carbonate,  or  phosphate.  The  specific  gravity 
of  kaolin  is  2.3.  If  fused  with  six  times  its  weight  of  caustic 
potash,  the  resulting  mass  gives  up  potassium  aluminate  when 


washed  with  water,  An  analogous  result  is  obtained  with 
sodium  carbonate.  Grabau  has  prepared  very  pure  aluminium 
fluoride  from  kaolin  by  the  use  of  sulphuric  acid  and  subse- 
quent boiling  with  fluorspar. 

Large  deposits  of  kaolin  are  found  in  many  parts  of  the 
world.  The  best  locality  in  Europe  is  near  Limoges,  France, 
with  which  the  famous  Sevres  porcelain  is  made.  Large  beds 
are  found  in  Cornwall  and  West  Devon,  England.  In  the 
United  States  the  largest  deposits  are  at  Wilmington,  Del.,  and 
in  South  Carolina,  Georgia  and  Alabama.  These  deposits  are 
worked  extensively,  and  the  product  used  by  the  pottery, 
paper,  cotton,  and  various  other  industries.  The  value  at  the 
mines  is  very  small,  it  not  costing  over  $0.50  per  ton  to  mine 
it,  but  for  many  purposes  it  must  be  crushed,  washed,  and  even 
floated,  which  increases  its  value  to  $5  or  $10  a  ton  in  New 
York  city. 

The  purity  of  kaolin,  and  the  almost  inexhaustible  beds  in 
which  it  occurs,  stamp  it  as  the  natural  ore  of  aluminium.  All 
that  is  needed  is  a  cheap  process  for  separating  the  pure  alu- 
mina from  the  silica,  in  which  case  no  other  mineral  could 
compete  with  it  as  the  main  staple  of  the  aluminium  industry. 
This  is  a  promising  field  for  chemical  experimenters,  for  such 
a  process  would  be  of  great  value. 

Common  clays  are  either  very  impure  kaolin,  or  else  they 
contain  chemically  a  much  larger  proportion  of  silica.  The 
percentage  of  silica  may  range  from  50  per  cent,  up  to  70  per 
cent,  while  that  of  the  alumina  present  ranges  downwards  from 
35  to  15  per  cent.  These  common  clays  are  far  too  impure 
and  low  in  silica  to  serve  as  a  source  of  aluminium,  and  in  no 
case  could  they  compete  with  kaolin. 

Some  anhydrous  silicates  of  aluminium  are  found  in  nature, 
such  as  Disthene,  Andalusite  and  Cyanite,  whose  formula  is 
AUOj.SiOj,  containing  62.5  per  cent,  of  alumina ;  but  they  do 
not  occur  in  large  quantities,  and,  even  if  they  did,  are  so  hard 
and  difficult  to  decompose  that  they  would  never  be  preferred 
to  kaolin. 

50  aluminium. 

Native  Sulphate  of  Alumina. 

In  the  summer  of  1884,  a  large  deposit  of  rock  called  "  native 
alum"  was  discovered  on  the  Gila  River,  Socorro  County,  New 
Mexico,  about  two  miles  below  the  fork  of  the  Little  Gila,  and 
four  miles  below  the  Gila  Hot  Springs.  The  deposit  is  said  to 
extend  over  an  area  one  mile  square  and  to  be  very  thick  in 
places.  The  greater  part  of  the  mineral  is  impure,  as  is  usual 
with  native  occurrences,  but  it  is  thought  that  large  quantities 
are  available.  A  company  formed  in  Socorro  has  taken  up  the 
alum-bearing  ground.  Through  the  kindness  of  Mr.  W.  B. 
Spear,  of  Philadelphia,  the  author  was  enabled  to  get  a  speci- 
men of  the  mineral. 

It  is  white,  with  a  yellowish  tinge.  On  close  examination  it 
is  seen  to  consist  of  layers  of  white,  pure-looking  material  ar- 
ranged with  a  fibrous  appearance  at  right  angles  to  the  lamina- 
tion. These  layers  are  about  one-quarter  of  an  inch  thick. 
Separating  them  are  thin  layers  of  a  material  which  is  deeper 
yellow,  harder  and  more  compact.  The  whole  lump  breaks 
easily,  and  has  a  strong  alum  taste.  On  investigation,  the 
fibrous  material  was  found  to  be  hydrated  sulphate  of  alumina, 
the  harder  material  sulphate  of  lime.  Analysis  showed  7  to  8 
per  cent,  of  insoluble  material,  the  remainder  corresponding  to 
the  formula  Al2(S04)3.i8H20.  A  small  amount  of  iron  was 

State  Geologist  Waring  informs  the  writer  that  the  deposits 
occur  only  in  sheltered  spots  protected  from  the  rain,  that  the 
region  is  eruptive,  and  that  where  the  trachyte  rock  is  being 
decomposed  by  sulphuric  gases  and  waters,  the  salts  rise  to  the 
surface  and  form  crusts  in  protected  places.  Often  the  earth 
contains  10  per  cent,  or  more  of  the  anhydrous  sulphate. 

A  similar  mineral  occurs  in  Purgatory  Valley,  12  miles  east  of 
Trinidad,  Colorado. 

A  variety  of  the  same  mineral  containing  some  silica  was 
found  in  a  stratum  25  feet  thick  by  the  Congo  Coal  Company, 
while  sinking  a  shaft  at  Congo,  Ohio,  in  1893.  An  analysis  of 
this  by  Dr.  Lisle,  of  Springfield,  Ohio,  gave 


Alumina 50.16  per  cent. 

Silica 28.98       " 

Lime 0.46       " 

Sulphuric  acid 16.21        " 

Water 4.28       " 

These  minerals  would  appear  to  ofifer  a  cheap  source  of 
alumina,  as  the  operations  necessary  for  treating  them  are  very- 
simple,  being  solution  in  warm  water,  filtration,  evaporation, 
and  roasting.  The  excessive  freight  charges  are  against  the 
New  Mexico  and  Colorado  deposits,  but  that  in  Ohio  should 
be  of  considerable  economic  importance  if  the  reports  concern- 
ing its  extent  are  verified. 



Commercial  aluminium  is  never  chemically  pure,  and  there- 
fore displays  properties  varying  more  or  less  from  those  of  the 
pure  .metal  according  to  the  character  and  amount  of  impurities 
present.  In  this  treatise,  whenever  the  properties  of  aluminium 
are  mentioned,  they  must  be  understood  to  refer  to  the  chemi- 
cally pure  metal,  and  not  to  the  commercial  article,  unless  spe- 
cifically stated. 

The  impurities  most  frequently  present  in  commercial  alu- 
minium are  iron  and  silicon.  These  are  found  in  all  brands, 
varying  in  amount  from  i  per  cent,  in  the  purest  to  6  and  even 
8  per  cent,  in  the  worst.  Besides  these,  various  other  impuri- 
ties are  found  coming  from  accidental  sources  in  the  manufac- 
ture ;  thus,  some  of  the  first  metal  made  by  Deville  contained 
a  large  amount  of  copper  (Analysis  i),  coming  from  boats  of 
that  metal  which  he  used  in  his  experiments.  Metal  made 
later  by  Deville  contained  zinc,  coming  from  zinc  muffles  which 
he  had  borrowed  and  used  for  retorts,  old  retorts  broken  up 
having  been  used  in  the  composition  of  the  new  ones.  More 
recently,  aluminium  has  been  produced  by  the  agency  of 
sodium  in  the  presence  of  lead,  which  latter  it  takes  up  in  small 
amount.  Sodium  is  liable  to  remain  alloyed  in  very  small  pro- 
portion, yet  it  is  an  element  so  easily  attacked  that  it  destroys 
some  of  the  most  valuable  qualities  of  the  aluminium.  The 
distinct  effect,  however,  of  each  of  these  usual  impurities  in 
modifying  the  physical  properties  of  aluminium  has  not  yet 
been  investigated  in  a  thoroughly  satisfactory  manner.  A  few 
years  more,  however,  of  increasing  familiarity  with  and  hand- 
ling of  the  metal  on  a  large  commercial  scale  will,  I  believe, 



cause  the  effect  of  foreign  elements  on  aluminium  to  be  as 
plainly  recognized  as  is  now  the  case  with  carbon  and  the 
metalloids  in  iron.  In  general,  we  may  say  that  silicon  seems 
to  play  a  role  in  aluminium  closely  analogous  to  that  of  carbon 
in  iron ;  the  purest  aluminium  is  fibrous  and  tough,  but  a  small 
percentage  of  silicon  makes  it  crystalline  and  brittle.  Further- 
more, a  considerable  proportion  occurs  in  the  graphitoidal 
state,  and  may  be  separately  estimated  as  graphitoidal  silicon 
by  dissolving  the  metal  in  dilute  hydrochloric  acid  in  the  pres- 
ence of  bromine  water.  A  small  amount  of  silicon,  however,, 
gives  pure  aluminium  a  bluish  cast,  a  disagreeable  smell,  and 
greatly  lessens  its  resistance  to  corroding  agents.  A  small 
proportion  of  iron  makes  the  metal  denser  and  stronger,  but  a 
quantity  above  i  per  cent,  quickly  makes  it  brittle.  A  small 
quantity  of  copper  whitens  aluminium,  makes  it  much  stronger 
and  lessens  its  shrinkage  in  casting,  but  with  over  5  per  cent, 
it  becomes  brittle. 

As  aluminium  was  made  by  the  sodium  processes,  it  con- 
tained as  impurity  about  equal  quantities  of  iron  and  silicon  ;  as 
made  by  the  electrolytic  processes,  the  iron  present  is  usually 
much  less  than  the  silicon.  Carbon  can  only  exist  in  alumin- 
ium that  has  been  subjected  to  an  intense  heat,  such  as  in  an 
electric  furnace,  when  it  may  be  absorbed  in  small  quantity, 
and  makes  the  metal  brittle ;  it  does  not  occur,  however,  in 
ordinary  commercial  aluminium.  Titanium  may  occur  in 
aluminium  made  from  raw  bauxite,  which  frequently  contains 
titanic  oxide ;  its  presence  in  small  amount  makes  the  metal 
much  stronger,  but  gives  it  a  bluish  tint.  There  is  needed  a 
systematic  investigation  of  the  effect  of  small  amounts  of  impuri- 
ties on  the  physical  and  chemical  properties  of  pure  aluminium. 

The  following  analyses  are  of  considerable  historic  interest  as 
showing  incidentally  the  improvement  which  has  been  made  in 
the  quality  of  the  commercial  metal  since  the  beginning  of  the 
industry : 




1.  Deville  Process 88.350 

2.  "  "        92.500 

3.  "  "        92.000 

4.  "  "        92.969 

5.  "  "        94-700 

6.  "  "       96.160 

7.  Tissier  Bros 94.800 

8.  Morin  &  Co.,  Nanterre 97.200 

9.  "  "         97.000 

10.  "  "         98.290 

11.  "  "         97.680 

12.  Merle  &  Co.,  Salindres 96.253 

13.  "  "         96.890 

14.  "  "         97-400 

15.  "  "         97.600 

16.  Frishmuth 97-49 

17-  "  97-75 

18.  Hall's  Process 98-34 

19.  Deville-Castner - .  99.20 

20.  Grabau  Process  99.62 

21.  "  "         99-So 

22.  Hall's  Process 99-93 


























.  3-293 



1. 00 


















Notes  on  the  above  analyses :- 











12, 13. 

14. 15- 


Analyzed  by  Salvetat.    Contained  also  6.38  per  cent,  of  copper  and  a  trace 

of  lead. 
Analyzed  by  Dumas. 
Parisian  aluminium  bought  in  La  Haag, 
Analyzed  by  SalvStat.     Contained  also  a  trace  of  sodium. 
Parisian  aluminium  bought  in  Bonn  and  analyzed  by  Dr.  Kraut. 
Made   at   the  works  near  Rouen,  in  1858,  from  cryolite.     Analyzed   by 

Analyzed  by  Sauerwein.     Contained  also  traces  of  lead  and  sodium. 
Analyzed  by  Morin.     Average  of  several  months'  work. 
Analyzed  by  Kraut.     Represents  the  best  product  of  the  French  works 

sent  to  the  London  Exhibition  in  1862. 
Analyzed  by  Mallet.     The  best  metal  v/hich  could  be  bought  in  1880. 

Purchased  in  Berlin  by  Mallet,  and  used  by  him  as  the  material  which 

he  purified  and  used  for  determining  the  atomic  weight  of  aluminium. 
Analyzed  by  Hampe.     This  was  the  purest  metal  which  could  be  bought 

in  1876.     No.  14  contained  also  per  cent,  of  copper  and  0.20  per 

cent,  of  lead.     No.  15  contained  0.40  per  cent,  of  copper  and  0.20  per 

cent,  of  lead. 
Bought  in  Philadelphia  as  Frishmuth's  aluminium,  in  1885,  and  analyzed 

by  the  author. 


17.  Specimen  of  the  metal  composing  the  tip  of  the  Washington  Monument, 

cast  by  Frishmuth.     This  analysis  is  reported  by  R.  L.  Packard  m  the 
Mineral  Resources  of  the  United  States,  1883-4. 

18.  The  best  ordinary  grade  of  metal  made  by  this  process,  analyzed  by  Hunt 

&  Clapp,  Pittsburgh.     For  average  analyses,  etc.,  see  description  of  pro- 

19.  The  best  grade  made  by  this  process,  exhibited  at  the  Paris  Exposition, 

1889.     Analyzed  by  CuUen. 

20.  Analysis  by  Dr.  Kraut  of  metal  being  made  on  a  commercial  scale. 

21.  Analysis  by  Grabau  of  the  purest  metal  yet  obtained  by  his  process. 

22.  Made  from  chemically  pure  alumina,  in  order  to  determine  what  degree  of 

purity  was  attainable  by  the  electrolytic  processes. 

In  addition  to  the  above,  the  following  analyses  made  in  the 
Pittsburgh  Testing  Laboratory  show  the  quality  of  commercial 
aluminium  which  has  been  put  on  the  market  in  recent  years : 

Com-  Graphi- 

Alumin-  bined  toidal 

Second  Quality  Metal.                      ium.  Silicon.  Silicon.  Iron.  Copper.  Sodium.  Lead. 

Pittsburgh  Reduction  Co 9S-00  1.50  1.35  2.00  0.07  0.04  0.03 

Society  Anon,  de  TAluminium  ..  95.00  0.90  i.oo  3.00  0.05  o.oi  0.04 

Alliance  Aluminium  Co 95-00  0.90  0.75  3.25  0.02  0.07  o.oi 

The  Aluminium  Co.,  Limited  . . .  95.00  0.85  0.75  3.00  0.30  nil 

The  Al.  LA.  G.,  Switzerland  ...  95.00  1.75  1.15  2.00  0.07  nil 

"            "                  "            ...  94.15  1.02  0.54  2.80  1.49  —  — 

First  Quality  Metal. 

Pittsburgh  Reduction  Co 97.00  1.55  1.25  0.13  0.03  0.02  0.02 

Soc.  Anon,  de  I'Al 97.00  0.90  0.82  1.20  0.04  o.oi  0.03 

Alliance  Al.  Co.,  Ltd 97.00  0.95  0.53  1.45  0.01  0.05  o.oi 

The  Al.  Co.,  Limited 97.00  0.75  0.52  1.55  0.03  0.15  nil 

Pittsburgh  Reduction  Co 98.00  1.30  0.60  0.07  o.oi  o.oi  o.oi 

Soc.  Anon,  de  I'Al 98.00  0.71  0.35  0.90  o.oi  o.oi  0.02 

Alliance  Al.  Co.,  Ltd 98.00  0.90  0.29  0.75  o.oi  0.04  o.oi 

The  Al.  Co.,  Limited 98.00  0.90  0.23  0.80  0.02  0.05  nil 

Pittsburgh  Reduction  Co 98.52  0.42  0.72  0.05  0.06  nil  0.04 

"                 "           "    99.00  0.80  0.15  0.03  O.OI  nil  O.OI 

Soc.  Anon,  de  I'Al 99-00  0.35  0.13  0.50       nil  o.oi  o.oi 

Alhance  Al.  Co.,  Ltd 99.00  0.31  0.20  0.45        nil  0.03  o.oi 

The  Al.  Co.,  Limited 99-°°  °-^l  °-'S  o-5S  °-°2  o.oi  nil 

Pittsburgh  Reduction  Co 99-20  041  0.34  0.05        nil  nil  nil 

Alliance  Al.  Co.,  Ltd 99- H  o-23  0.17  0.46        nil  nil  nil 

Pittsburgh  Reduction  Co 99-34  °A°  0-21  0.05        nU  nil  nil 

The  makers  represented  above  are : 

The  Pittsburgh  Reduction  Company.     New  Kensington,  Pa. 


The  Alliance  Aluminium  Company,  Limited.  Wallsend-on- 
Tyne,  England. 

The  Aluminium  Company,  Limited.  Oldbury,  near  Birming- 
ham, England. 

The  Societe  Anonyme  de  I'Aluminium.    Nanterre,  France. 

The  Aluminium  Industrie  Actien-Gesellschaft.  Neuhausen, 

The  second,  third  and  fourth  of  these  firms  used  the  sodium 
process,  the  others  the  electrolyic  methods.  It  is  at  once  seen 
that  for  metal  with  the  same  proportion  of  aluminium,  that 
made  by  the  electrolytic  processes  contains  less  iron,  but  more 
silicon,  than  that  made  by  the  sodium  processes ;  there  is  no 
observable  regularity  in  the  proportion  of  combined  and  graph- 
itoidal  silicon  to  the  amount  of  iron.  On  an  average,  the  graph- 
itoidal  silicon  is  about  one-third  to  two-thirds  of  the  combined 

Rammelsberg  (Kerl's  Handbuch)  investigated  the  question 
of  the  different  states  of  silicon  in  aluminium.  He  found  in 
aluminium  reduced  from  cryolite  by  sodium  in  a  porcelain  cru- 
cible, that  on  treatment  with  hydrochloric  acid,  the  combined 
silicon  changes  into  silica,  or  part  escapes  as  silicon  hydride, 
while  the  graphitoidal  silicon  remains  as  a  black  residue.  Two 
analyses  gave  him  the  following  results : 

1..  2. 

Silicon  obtained  as  silica 9.55  1.85 

Free  silicon 0.17  0.12 

Silicon  escaping  in  SiH'' 0.74  0.58 

In  aluminium  containing  6.20  per  cent,  of  total  silicon,  ana- 
lyzed in  the  Pittsburgh  Reduction  Co.'s  laboratory,  3.85  per 
cent,  was  graphitoidal  silicon.  In  another  specimen,  contain- 
ing 5 -30  per  cent,  of  total  silicon,  2.40  per  cent,  was  graphi- 

An  experiment,  made  at  the  Pittsburgh  Testing  Laboratory, 
to  determine  the  influence  of  quick  or  slow  cooling  on  the  con- 
dition of  the  silicon,  showed  that  the  chilled  metal  contained, 
slightly  more  of  the  silicon  in  the  graphitoidal  state  and  less  in 
the  combined  state  than  metal  slowly  cooled. 


This  result  is  the  opposite  of  the  behavior  of  carbon  in  iron, 
and  it  is  found,  as  might  be  expected,  that  no  appreciable  dif- 
ference in  hardness  can  be  detected  between  the  surfaces  of 
ingots  cast  in  chills  and  those  cast  in  hot  moulds. 

M.  Dumas  found  that  aluminium  usually  contains  gases, 
about  which  he  makes  the  following  statements:*  On  submit- 
ting aluminium  in  a  vacuum  to  the  action  of  a  gradually  increas- 
ing temperature  up  to  the  softening  point  of  porcelain,  and 
letting  the  mercury  pump  continue  acting  on  the  retort  until  it 
was  completely  exhausted,  considerable  quantities  of  gas  were 
withdrawn.  The  liberation  of  the  gas  from  the  metal  seems  to 
take  place  suddenly  towards  a  red-white  heat.  200  grammes 
of  aluminium,  occupying  80  c.c,  gave  89.5  c.c.  of  gas,  meas- 
ured at  17°  and  755  mm.  pressure.  The  gas  consisted  of  1.5 
c.c.  carbonic  acid,  and  88  c.c.  hydrogen.  Carbonic  oxide, 
nitrogen  and  oxygen,  were  absent. 

The  author  has  observed  that  molten  aluminium  will  absorb 
large  quantities  of  gas.  On  passing  sulphuretted  hydrogen 
into  the  melted  metal  for  about  twenty  minutes  some  aluminium 
sulphide  was  formed,  while  the  metal  appeared  to  absorb  the 
gas.  On  pouring,  the  metal  ran  very  sluggishly,  with  a  thick 
edge,  but  when  just  on  the  point  of  setting,  gas  was  disengaged 
so  actively  that  the  crackling  sound  could  be  heard  several  feet 
away,  and  the  thick  metal  became  suddenly  quite  fluid  and 
spread  over  the  plate  in  a  thin  sheet.  The  gas  disengaged 
seemed  by  its  odor  to  contain  a  large  proportion  of  sulphur- 
etted hydrogen,  although  free  hydrogen  may  have  been  pres- 
ent in  it. 

Le  Verrier  has  established  the  presence  of  carbon  in  small 
amount  in  commercial  aluminium.!  Taking  a  large  quantity  of 
metal  and  treating  it  with  a  current  of  hydrochloric  acid  or 
hydriodic  acid  gas,  entirely  free  from  oxygen,  there  remains  a 
grey  residue.  This,  treated  with  dilute  hydrochloric  acid,  gives 
a  very  light  residue  of  amorphous  carbon,  of  a  maroon  color, 

*  Comptes  Rendus,  xc,  1027  (1880). 
t  Comptes  Rendus,  July,  1894,  p.  14. 


■which,  on  being  separated  out,  can  be  entirely  burnt  to  car- 
bonic acid  gas  in  a  current  of  oxygen.  This  carbon  does  not 
contain  a  trace  of  graphite ;  it  is  entirely  amorphous.  It  is 
easiest  estimated  by  dissolving  ten  grammes  of  aluminium  in  a 
concentrated  solution  of  caustic  potash,  washing  the  residue 
with  water,  drying,  burning  in  a  current  of  oxygen,  and  weigh- 
ing the  carbonic  acid  formed.  In  three  specimens  tested  there 
were  found  0.104,  O.108  and  O.080  per  cent,  of  carbon  respect- 
ively. To  determine  the  effect  of  carbon  on  the  physical  prop- 
erties of  aluminium,  he  melted  best  quality  metal,  cast  a 
specimen  ingot,  and  then  dissolved  in  it  some  crystallized 
aluminium  carbide,  AhCs  (for  method  of  making  this  see  Chap- 
ter XIV) .  A  specimen  of  the  carburized  metal  was  then  cast 
and  tested.  The  results  were  as  follows;  the  weights  being  per 
square  millimetre  of  section  : 

Cast  Specimens. 

Elastic  Limit.  Breaking  Load.  Elongation. 

Pure  aluminium —  1 1. 1  kilos.  9  per  cent. 

Carburized  aluminium —  6.5     "  5       " 

—  8.6    "  3       " 

Rolled  Specimens. 

Elastic  Limit.  Breaking  Load.  Elongation. 

Pure  aluminium,  hard 23     kilos.  25.0    kilos.  2.0  per  cent. 

"  "  annealed 8        "  14.0        "  23.0       " 

Carburized  aluminium,  hard 20        "  20.79     "  2.5       " 

"  "  annealed 7.7     "  13.80      "  26.5       " 

It  would  appear  that  the  cast  metal  shows  the  greatest  de- 
terioration by  the  presence  of  carbon. 

Le  Verrier  also  proved  the  presence  of  traces  of  nitrogen  in 
commercial  aluminium  by  passing  the  hydrogen  evolved  during 
solution  in  dilute  caustic  potash  into  a  Nessler  solution,  which 
then  gives  the  ammonia  reaction.  To  determine  the  exact 
effect  of  nitrogen,  some  aluminium  was  melted  and  a  current  of 
nitrogen  passed  into  it.  The  metal  became  saturated  with  the 
gas,  and  showed  the  following  diminution  in  strength : 


Cast  Specimens. 

Elastic  Limit,  Breaking  Load.  Elongation. 

Pure  aluminium   7.5  kilos.  i I.I  kilos.  9  per  cent. 

Aluminium  saturated  with  nitrogen 6.5     "  g.6     "  6      " 

Le  Verrier  considers  that  nitrogen  and  carbon  occur  in  alu- 
minium in  the  state  of  aluminium  nitride  and  carbide  re- 
spectively, dissolved  in  the  excess  of  aluminium.  The  same 
investigator  has  discovfered  by  the  microscope,  in  the  residue 
left  by  dissolving  in  hydrochloric  acid,  very  small,  sharp  crys- 
tals of  boron  carbide,  the  boron  coming  from  the  boric  acid 
used  in  agglomerating  the  carbon  electrodes.  A  little  amor- 
phous alumina  is  also  sometimes  to  be  found. 


Deville :  The  color  of  aluminium  is  a  beautiful  white  with  a 
slight  blue  tint,  especially  when  it  has  been  strongly  worked. 
Being  put  alongside  silver,  their  color  is  sensibly  the  same. 
However,  common  silver,  and  especially  that  alloyed  with 
copper,  has  a  yellow  tinge,  making  the  aluminium  look  whiter 
by  comparison.  Tin  is  still  yellower  than  silver,  so  that  alu- 
minium possesses  a  color  unlike  any  other  useful  metal. 

Mallet:  Absolutely  pure  aluminium  is  perceptibly  whiter 
than  the  commercial  metal ;  on  a  cut  surface  very  nearly  pure 
tin- white,  without  bluish  tinge,  as  far  as  could  be  judged  from 
the  small  pieces  examined. 

The  purest-looking  aluminium  examined  by  the  author  is 
that  made  by  Grabau.  On  a  fresh  fracture  it  is  absolutely 
■white,  but  on  long  exposure  to  the  air  it  takes  a  faint,  almost 
imperceptible  bluish  tint.  On  a  cut  surface  it  has  the  faintest 
suspicion  of  a  yellow  tint,  not  so  decided  as  the  yellowish  color 
of  pure  tin.  Ordinary  commercial  aluminium  is  bluish  on  a 
fresh  fracture,  the  tint  being  deeper  the  greater  the  amount  of 
impurities  it  contains.  A  specimen  with  10  per  cent,  of  silicon 
and  5  per  cent,  of  iron  was  almost  as  blue  as  lead.  It  is  my 
belief  that  a  very  small  percentage  of  copper  closes  the  grain 
-and  whitens  the  fracture  a  little;   I  have  also  found  that  chilling 


suddenly  from  a  high  temperature  has  the  same  effect.  Wheir 
ingots  of  aluminium  are  exposed  a  long  time  to  damp  air,  the 
thin  film  of  oxide  forming  on  them  gives  a  more  decided  bluish 
cast  to  the  metal,  since  the  coating  is  perfectly  snow-white  and 
hence,  by  contrast,  heightens  the  bluish  tint  of  the  metallic 
background.  Mourey  recommended  removing  this  discolora- 
tion by  placing  the  articles  first  in  dilute  hydrofluoric  acid, 
1,000  parts  of  water  to  2  of  acid,  and  afterwards  dipping  in 
nitric  acid.  The  oxide  would  thus  be  dissolved  and  the  original 
color  restored.  Pure  aluminium  possesses  to  the  highest  de- 
gree that  property  expressed  best  by  the  French  term  "  eclat." 
It  is  rather  difficult  to  see  why  the  blue  tint  should  be  more 
prominent  after  the  metal  has  been  worked,  yet  I  think  two 
reasons  will  explain  this  phenomenon ;  first,  aluminium  is  not  a 
hard  metal,  and  on  polishing  or  burnishing,  particles  of  dirt  or 
foreign  substances  are  driven  into  the  pores  of  the  metal,, 
thereby  altering  its  color  slightly ;  second,  any  metal  looks 
whiter  when  its  surface  is  slightly  rough  than  when  highly 
polished,  in  the  latter  case  it  being  as  much  the  reflected  color 
of  the  general  surroundings  as  the  color  of  the  metal  itself 
which  is  seen.  I  have  never  seen  any  highly  polished  white 
metal  which  did  not  look  bluish,  especially  when  reflecting  out- 
door light.  I  think  this  explains  why  opera-glasses,  rings, 
jewelry,  etc.,  generally  look  bluer  than  the  bar  or  ingot-metal 
from  which  they  are  made. 

Aluminium  takes  a  very  beautiful  mat,  which  keeps  almost 
indefinitely  in  the  air,  the  surface  thus  slightly  roughened  ap- 
pearing much  whiter  than  the  original  polished  surface.  Alu- 
minium can  be  polished  and  burnished  without  much  difficulty 
if  attention  is  given  to  a  few  particulars  which  it  is  necessary  to 
observe.     (For  methods  of  poHshing,  etc.,  see  Chapter  XIII.) 

Extremely  thin  films  of  aluminium  are  fine  violet-blue  by 
transmitted  light. 


A  cast  ingot  of  purest  aluminium  has  a  slightly  fibrous 
structure,  a  section   y^    inch   thick  bending  twenty  degrees  or 


SO  from  a  straight  line  when  sharply  bent  before  showing  cracks 
at  the  outside  of  the  turn.  The  fracture  of  such  an  ingot  is 
uneven,  rough,  and  very  close,  often  showing  a  curious  semi- 
fused  appearance,  as  if  it  had  been  already  exposed  to  heat  and 
the  sharpest  points  melted  down.  However,  only  the  purest 
varieties  show  these  peculiarities.  Metal  containing  96  to  97 
per  cent,  of  aluminium  begins  to  show  a  crystalline  structure, 
breaks  short,  and  with  a  tolerably  level  surface.  Metal  less 
than  95  per  cent,  pure  shows  large  shining  crystal  surfaces  on 
the  fracture,  the  smaller  crystals  being  on  the  outside  of  the 
ingot  where  it  has  been  cooled  most  quickly,  while  in  the  cen- 
tre the  crystalline  surfaces  may  be  as  large  as  tV  inch  in 
diameter.  A  specimen  containing  only  85  per  cent,  of  alumin- 
ium broke  as  short  as  a  bar  of  antimonial  lead,  with  a  large 
granular,  crystalline  surface. 

Working  the  metal  increases  its  fibrousness  greatly,  the  sec- 
tion of  a  square  rolled  bar  of  good  metal  looking  very  much 
like  that  of  a  low-carbon  steel. 


The  purest  aluminium  is  distinctly  softer  than  the  commer- 
cial ;  estimated  on  the  scale  of  hardness  proposed  by  Mohs  it 
would  be  written  as  about  2.5,  that  is,  a  little  harder  than  can 
be  scratched  by  the  nail.  It  is  not  so  soft  as  pure  tin.  The 
presence  of  impurities,  however,  rapidly  increases  the  hardness. 
While  99  per  cent,  aluminium  can  be  cut  smoothly  with  the 
knife  and  shavings  turned  up  almost  as  with  pure  tin,  yet  95 
per  cent,  metal  can  hardly  be  cut  at  all ;  the  shavings  break  off 
short,  and  a  fine  grating  is  felt  through  the  blade. 

Aluminium  becomes  surface  hardened  by  cold  working. 
Castings  of  aluminium  drop-forged  cold,  in  dies,  are  made 
sensibly  harder  and  thus  adapted  for  standing  more  wear. 
Cold  drawing  or  rolling  gives  to  it  nearly  the  hardness  of  brass. 
In  a  drop  test  to  investigate  this  quality  made  in  the  Pittsburgh 
Testing  Laboratory,  the  following  comparative  results  were 
reached : 



Aluminium,  rolled 62 

Aluminium,  cast 47 

Brass,  rolled   86 

Brass,  cast 71 

Copper 100 

Experience  in  testing  various  specimens  of  commercial  alu- 
minium with  the  knife  will,  I  am  sure,  enable  a  person  to  be- 
come quite  skillful  in  determining  the  purity  and  in  separating 
different  grades  from  each  other.  Taking  this  test  in  connec- 
tion with  the  breaking  and  surface  of  fracture,  it  appears  to  me 
that  these  indications  are  as  significant  and  can  be  made  of  as 
much  use  as  the  corresponding  tests  for  iron,  steel,  and  other 
metals.  Mr.  Joseph  Richards,  the  author's  father,  having  had 
many  years'  experience  in  testing  lead,  tin,  zinc,  and  similar 
metals,  in  which  the  knife-blade  has  been  put  to  good  service, 
has  been  able  with  very  little  practice  to  arrange  a  number  of 
specimens  of  aluminium  correctly  according  to  their  purity  sim- 
ply by  noting  carefully  the  way  they  cut  and  the  color  of  the 
cut  surface.  These  tests  will  in  the  future,  I  am  sure,  be  of 
great  use  to  those  handling  aluminium  on  a  large  scale,  es-- 
pecially  in  the  works  where  it  is  produced. 

Specific  Gravity. 

Mallet:  The  specific  gravity  of  absolutely  pure  aluminium- 
was  carefully  determined  at  4°  C,  and  the  mean  of  three 
closely  agreeing  observations  gave  2.583. 

Commercial  aluminium  is  almost  always  heavier  than  this, 
but  the  increase  is  not  in  direct  proportion  to  the  amount  of 
impurities  present.  There  are  two  reasons  why  this  last  state- 
ment is  correct;  first,  we  cannot  say  what  expansion  or  con- 
traction may  take  place  in  forming  the  alloy;  second,  while- 
most  of  the  impurities  which  occur  are  much  heavier  than  alu- 
minium, yet  silicon,  the  most  frequent  of  all,  has  a  specific 
gravity  of  only  2.34  (Deville's  determination),  and  therefore 
acts  in  the  opposite  direction  to  the  other  impurities,  though. 


not  to  SO  great  an  extent.     The  following  analyses  and  specific 
gravities  may  give  some  information  on  this  point:  — 


Specific  Gravity. 










2.61  (2.64) 





2.61  (2.69) 





2.59  (2.74) 






It  is  seen  in  each  case  that  the  calculated  specific  gravity  is. 
much  less  than  the  observed,  which  would  show  contraction  in 
volume  by  alloying.  Indeed,  this  is  a  prominent  characteristic 
of  aluminium  alloys,  aluminium  often  taking  up  several  per 
cent,  of  its  weight  of  another  metal  without  its  volume  being 
increased,  the  particles  of  the  other  metal  seeming  to  pass  be- 
tween those  of  the  aluminium ;  thus  probably  accounting  for 
the  extraordinary  strength  and  closeness  of  many  of  the  alumin- 
ium alloys.  This  subject  is  treated  more  at  length  in  the  chap- 
ter on  alloys.  We  can  see  the  large  contraction  taking  place 
by  inspecting  the  numbers  in  parentheses  under  the  heading 
"Calculated."  These  are  computed  on  the  supposition  that 
the  volume  of  the  impure  aluminium  is  equal  to  that  of  the 
pure  aluminium  entering  into  it.  As  these  numbers  are  also- 
less  than  the  observed  specific  gravities,  the  extraordinary  fact 
is  shown  that  aluminium  can  absorb  several  per  cent,  of  iron 
and  silicon  and  yet  will  decrease  in  volume  in  doing  so. 

The  remarks  thus  far  made  are  based  on  the  gravity  of  cast 
metal.  Aluminium  increases  in  density  by  being  worked  :  De- 
ville  states  that  metal  with  a  specific  gravity  of  2.56  had  this 
increased  to  2.67  by  rolling,  which,  he  says,  may  explain  the 
diflerences  existing  in  its  properties  after  being  annealed  or 
worked.  He  remarked  further  that  heating  this  rolled  metal  to 
100°,  and  cooling  quickly,  changed  its  specific  gravity  very  little, 
lowering  it  to  2.65.  I  have  observed  that  on  heating  a  piece  of 
aluminium  almost  to  its  fusing  point  and  suddenly  chiUing  it  in 
water,  its  specific  gravity  was  lowered  from  2.73  to  2.69. 


Experiments  made  by  Prof.  J.  W.  Langley  with  aluminium 
98.52  per  cent,  pure,  the  rest  being  mostly  silicon,  gave  its 
specific  gravity  as  follows  : 

Sample  sawn  from  centre  of  a  cast  ingot 2.587 

Same,  annealed 2.692 

Rolled  into  sheet  0.0625  inch  thick   2.710 

Stamped  into  medals 2.725 

The  low  specific  gravity  of  aluminium,  when  compared  with 
that  of  the  other  metals,  is  (in  the  words  of  a  recent  lecturer) 
"  the  physical  property  on  which  our  hopes  of  the  future  use- 
fulness of  aluminium  chiefly  rest."  The  following  table  will 
facilitate  this  comparison : 

Specific  Gravity. 

Alumin-  Founds  in  a  Kilos  in  .1 

Water  =  I.  ium  =:  i.  cubic  foot.  cubic  meter. 

Platinum 21.5               8.3  1344  21,500 

Gold 19.3                7.4  1206  19,300 

Lead 11.4               4.6  712  11,400 

Silver 10.5                4.0  656  10,500 

Copper 8.9               3.5  557  8,900 

Iron  and  steel 7.8               2.8  487  7,800 

Tin 7.3               2.7  456  7,300 

Zinc 7.1               2.7  444  7,100 

Aluminium 2.6               i.o  163  2,600 

In  comparing  the  price  of  aluminium  with  that  of  a  metal 
which  it  might  replace,  for  purposes  where  the  bulk  of  the  arti- 
cle is  fixed,  it  is  of  first  importance  to  take  this  low  specific 
gravity  into  account.  When  we  come  to  consider  closely,  we 
find  that  almost  every  article  of  use  or  ornament  is  wanted  of  a 
fixed  size,  and  therefore  the  real  basis  of  comparison  of  prices  is 
that  of  a  fixed  volume  of  the  metal  rather  than  a  fixed  weight. 
To  facilitate  this  comparison,  I  give  below  the  actual  market 
prices  of  one  pound  weight  of  the  common  metals,  with  the 
prices  of  equal  volumes: 


Value  of       Relative  cost  Value  of  Relative  cost 

I  pound,    of  equal  weights,     i  cubic  foot,    of  equal  volumes. 

Silver jSio.oo  2850  ;J656o.oo          1 1430 

Nickel 0.50  140  279.00  468 

Aluminium 0.35  100  S7-S0  10° 

German  silver 0.30  85  167,00  290 

Tin 0.15  43  68.50  120 

Bronze 0.15  43  79.00  137 

Brass    0.12  34  61.75  107 

Copper  28  55.75  97 

Lead 0.04  11  28.50  50 

Zinc 0.04  II  17-75  3' 

Steel  0.02  6  9.75  17 

Cast  Iron o.oi  3  5.00  8 

It  is  therefore  evident,  that  for  almost  all  uses  to  which 
aluminium  is  applicable,  there  are  only  five  of  the  common 
metals  which  are  cheaper,  viz.,  copper,  lead,  zinc,  steel  and  cast- 
iron.  When  it  is  further  remembered  that  the  cost  of  the  metal 
alone  usually  forms  only  a  small  part  of  the  value  of  the  finished 
article,  it  can  be  further  asserted  that  there  should  be  only  a 
trifling  diflference  between  the  cost  of  an  article  made  in  alu- 
minium and  one  of  tin,  bronze,  brass  or  copper.  The  sole 
reason  why  aluminium  articles  are  not  sold  more  cheaply  at 
present,  lies  in  the  fact  that  they  are  not  made  and  sold  in  such 
large  quantities ;  the  increase  of  the  aluminium  industry  will 
therefore  ensure  lower  prices  for  aluminium  goods. 


Deville :  Aluminium  melts  at  a  temperature  higher  than  that 
of  zinc,  lower  than  that  of  silver,  but  approaching  nearer  to  that 
of  zinc  than  silver.     It  is,  therefore,  quite  a  fusible  metal. 

Mallet :  It  seems  that  pure  aluminium  is  a  Httle  less  fusible 
than  the  commercial  metal. 

Pictet  determined  the  melting  point  to  be  600°,  Heeren  about 
700°,  while  Van  der  Weyde  placed  it  as  high  as  850°.  On  a 
sample  containing  0.5  per  cent,  of  iron,  Carnelly  determined 
the  melting  point  at  700° ;  with  5  per  cent,  of  iron  it  did  not 
fuse  completely  until  730°.  The  discordance  between  these 
various  experimenters  lies  chiefly  in  the  errors  of  the  pyro- 


meters  used.  Since  the  perfection  of  the  electric  pyrometer  by 
Le  ChateHer,  the  melting  point  of  the  purest  aluminium  has 
been  repeatedly  observed  as  very  close  to  625°.  This  figure 
is  probably  correct  within  5°. 

A  very  small  admixture  of  iron  and  silicon  lowers  the  melt- 
ing point.  Le  Chatelier  found  with  a  metal  containing  1.50 
per  cent,  silicon  and  0.75  per  cent,  iron,  the  melting  point 
619°-  A  larger  quantity  of  either  of  these  elements  quickly 
operates  in  the  other  direction,  and  prevents  fluid  fusion  until 
a  temperature  above  625°  is  reached. 

Spring  has  determined  that  aluminium  powder  flows  to  a 
solid  mass  at  a  pressure  of  38  tons  per  square  inch,  at  ordinary 


Deville :  Aluminium  is  absolutely  fixed,  and  loses  no  part  of 
its  weight  when  it  is  violently  heated  in  a  forge  fire  in  a  carbon 

This  statement  was  made  in  1859,  and  can  still  be  accepted 
as  true  as  far  as  ordinary  furnace  temperatures  are  concerned. 
But,  with  the  use  of  the  electric  furnace,  temperatures  have 
been  attained  at  which  aluminium  does  sensibly  volatilize.  In 
Cowles  Bros,  electric  furnace  it  is  stated  that  the  aluminium  is 
almost  all  produced  as  vapor  and  as  such  is  absorbed  by  the 
copper  or  iron  present ;  when  these  are  not  present  it  is  found 
condensed  in  the  cooler  upper  part  of  the  furnace.  A  similar 
experience  has  been  met  in  other  electric  furnace  processes,  so 
that  the  volatilization  of  aluminium  at  these  extreme  tempera- 
tures may  be  accepted  as  a  fact. 

Aluminium  vapor  has  been  recently  produced  in  an  electric 
furnace  in  large  enough  amounts  to  determine  that  it  is  of  a 
green-blue  color. 

The  purest  aluminium  has  no  perceptible  odor,  but  metal 
containing  i  per  cent,  or  more  of  silicon  exhales  the  odor  of 
silicon  hydride,  exactly  the  same  odor  as  proceeds  from  cast 


iron.  Second  quality  commercial  aluminium  gives  this  smell 
quite  strongly,  but  in  the  present  first  quality  metal  it  is  difficult 
to  detect  it  except  by  smelling  immediately  after  a  brisk 

The  same  remark  may  be  made  regarding  taste  as  of  the 
odor.     The  purest  metal  has  no  taste ;  the  impure  tastes  like 
iron,  but  not  so  strongly. 


Deville,  as  also  Poggendorff  and  Reiss,  state  that  aluminium" 
is  very  feebly  magnetic.  It  must  be  remembered,  however,  that 
they  tested  metal  made  by  the  sodium  process,  which  almost 
invariably  contained  iron. 

Prof.  Frank  Very,  of  the  Allegheny  Observatory,  Allegheny, 
Pa.,  finds  aluminium  with  only  a  trace  of  iron  to  be  absolutely 
non-magnetic.  With  0.05  per  cent,  of  iron,  none  could  be  ob- 
served. An  ingot  containing  1.5  per  cent,  iron  showed  faint 
polarity,  while  with  2  per  cent,  the  polarity  was  very  decidedly 

Since  the  present  first  quality  commercial  aluminium  contains 
less  than  0.2  per  cent,  of  iron,  and  frequently  only  0.05  per 
cent.,  we  may  observe  that  this  is  less  than  is  usually  found  in 
commercial  brass,  bronze  or  german-silver,  and  for  this  reason, 
as  well  as  its  other  valuable  properties,  aluminium  answers  very 
well  for  compass  boxes  or  cases,  or  parts  of  electrical  instru- 
ments where  non-magnetic  properties  are  desired. 

Deville:  "A  very  curious  property,  which  aluminium  shows 
the  more  the  purer  it  is,  is  its  excessive  sonorousness,  so  that 
a  bar  of  it  suspended  by  a  fine  wire  and  struck  sounds  like  a 
crystal  bell.  M.  Lissajous,  who  with  me  observed  this  prop- 
erty, has  taken  advantage  of  it  to  construct  tuning  forks  of 
aluminium,  which  vibrate  very  well.  I  also  tried  to  cast  a  bell, 
which  has  been  sent  to  the  Royal  Institution  at  London  at  the 


request  of  my  friend  Rev.  J.  Barlow,  vice-president  and  secre- 
tary of  the  institution.  This  bell,  cast  on  a  model  not  well 
adapted  to  the  qualities  of  the  metal,  gives  a  sharp  sound  of 
considerable  intensity,  but  which  is  not  prolonged,  as  if  the 
clapper  or  support  hindered  the  sound,  which,  thus  hindered, 
becomes  far  from  agreeable.  The  sound  produced  by  the  in- 
gots is,  on  the  contrary,  very  pure  and  prolonged.  In  the  ex- 
periments made  in  Mr.  Faraday's  laboratory,  this  celebrated 
physicist  has  remarked  that  the  sound  produced  by  an  ingot  of 
aluminium  is  not  simple.  One  can  distinguish,  by  turning  the 
vibrating  ingot,  two  sounds  very  near  together  and  succeeding 
each  other  rapidly,  according  as  one  or  the  other  face  of  the 
ingot  faces  the  observer." 

The  bell  referred  to  above  was  20  kilos  in  weight  and  50 
centimetres  in  diameter,  but  as  Deville  admits,  its  sound  was 
not  pleasing,  and  a  contemporary  writer,  evidently  not  very 
enthusiastic  in  sounding  the  praises  of  aluminium,  said  that 
"  while  the  bell  was  highly  sonorous,  yet  it  gave  a  sound  like 
a  cracked  pot." 

I  have  not  heard  that  any  large  bell  has  since  been  cast,  but 
it  is  certain  that  the  metal  in  bars  has  a  highly  musical  ring. 
Faraday's  observation  has  also  been  verified,  for  a  recent  lec- 
turer suspended  by  one  end  a  bar  6  feet  long  31^  inches  wide, 
and  I  y^  inches  thick,  and  on  striking  it  a  prolonged  vibration 
ensued,  two  notes  being  recognized,  A  sharp  and  D  sharp,  the 
latter  more  subdued. 

Within  the  last  few  years  aluminium  has  been  extensively 
employed  for  sounding  boards  in  public  hails,  the  sounding 
boards  of  pianos,  and  even  for  the  construction  of  horns  and 
violins.  The  sounding  board  in  the  Lyceum  Hall,  New  York 
city,  is  an  example.  The  particular  advantage  is,  its  not  being 
affected  by  a  moist  atmosphere.  Dr.  Alfred  Springer,  of  Cin- 
cinnati, in  speaking  of  its  use  for  sounding  boards  says,*  "  It 
.differs  from  all  other  metals  in  the  absence  of  the  comparatively 

*  Trans.  A.  A.  Adv.  Science,  1891,  vol.  40,  p.  182. 


continuous  and  uniform  higher  partial  tones,  which  give  in 
other  metals  the  tone-color  called  "  metallic,"  and  further,  that 
it  also  possesses  an  elasticity  capable  of  sympathetic  vibration 
uniformly  through  a  wide  range  of  tone-pitch,  which  renders  it 
in  this  respect  superior  to  wood." 

Dufour  has  measured  the  velocity  of  sound  in  aluminium  at 
4950  metres  per  second,  almost  the  same  figure  as  for  steel. 

Crystalline  Form. 

Deville :  "  Aluminium  often  presents  a  crystalline  appearance 
when  it  has  been  cooled  slowly.  When  it  is  not  pure,  the  little 
crystals  which  form  are  needles,  and  cross  each  other  in  all 
directions.  When  it  is  almost  pure  it  still  crystallizes  by  fusion, 
but  with  difficulty,  and  one  may  observe  on  the  surface  of  the 
ingots  hexagons  which  appear  regularly"  parallel  along  lines 
which  centre  in  the  middle  of  the  polygon.  It  is  an  error  to 
conclude  from  this  observation  that  the  metal  crystallizes  in  the 
rhombohedral  system.  It  is  evident  that  a  crystal  of  the  regu- 
lar system  may  present  a  hexagonal  section;  while  on  the 
other  hand,  in  preparing  aluminium  by  the  battery  at  a  low 
temperature,  I  have  observed  complete  octahedrons  which  were 
impossible  of  measurement,  it  is  true,  but  their  angles  appeared 

By  slowly  cooling  a  large  body  of  melted  aluminium  and 
pouring  out  the  fluid  interior,  distinct  octahedrons  may  be 


Cast  aluminium  is  not  very  elastic;  it  may  be  likened  in  this 
respect  to  cast  silver.  When  worked,  however,  it  becomes 
more  rigid  and  elastic. 

Mallet  remarked  that  absolutely  pure  aluminium  seemed  to 
be  less  hardened  by  hammering  than  ordinary  commercial 

Cast  aluminium  stiffens  up  very  quickly  in  rolling  or  drawing, 
and   the  strains  set  up   in  the  metal  can  be  removed  by  an 


annealing,  which  consists  in  heating  the  metal  to  an  incipient 
red  heat  and  then  either  allowing  to  cool  slowly,  or  leaving  a 
few  minutes  at  that  heat  and  then  cooling  quickly  by  plunging 
into  water.  Metal  thus  treated  becomes  very  soft  and  pliable, 
hardly  any  more  elastic  than  lead,  and  will  stand  considerable 
working  before  it  again  becomes  stiff  and  elastic.  The  presence 
of  2  to  5  per  cent,  of  copper,  nickel,  silver,  German-silver  or 
titanium  increases  very  greatly  the  elasticity  of  aluminium 
without  increasing  noticeably  its  specific  gravity  or  impairing 
its  malleability. 

Tensile  and  Compressive  Strength. 

W.  H.  Barlow*  was  the  first  to  carefully  test  the  tensile 
strength  of  aluminium.  He  used  a  rolled  bar  one-quarter 
inch  square.  With -a  test  piece  two  inches  long,  the  tensile 
strength  was  found  to  be  26,800  pounds  per  square  inch,  with 
elongation  before  breaking  of  2.5  per  cent. 

Kamarschf  tested  aluminium  wire,  and  obtained  an  average 
of  12.5  kilos  per  square  millimetre,  equal  to  nearly  18,000 
pounds  per  square  inch.  This  wire  must  have  been  annealed, 
while  the  bar  tested  by  Barlow  was  worked  stiff  before  testing. 

Mr.  Spilsbury,  of  the  Trenton  Iron  Co.,  obtained  with  alu- 
minium wire  of  one-sixteenth  inch  diameter  a  tensile  strength 
of  62,300  pounds  per  square  inch,  the  wire  having  been  drawn 
with  one  annealing  from  a  wire-rod  one-sixth  inch  in  diameter. 
The  same  wire  made  47  bends  at  a  right  angle  before  breaking. 

A  most  valuable  series  of  mechanical  tests  of  aluminium 
have  been  made  by  the  Pittsburgh  Reduction  Company,  and 
are  copied  as  follows| : 

*  Rpt.  British  Assoc.  Adv.  Science,  1882,  p.  668. 

fDingler,  Vol.  172,  p.  55. 

J  Transactions  Am.  Inst.  Mining  Engineers.    Vol.  XVIII.,  p.  528  (1890). 

Tensile  Tests. 


No.  I  quality  commercial  metal,  averaging 
over  98  per  cent.  pure. 

Ordinary  castings  of  over  \  inch  sectional 

area,  as  cast .... 

Same,  annealed 

Same  castings,  hardened  by  drop  forging  cold 

Rolled  bars,  left  hard 

Same,  annealed 

Hammered  bars,  left  hard 

Same,  annealed 

"Wire  i  to  J  inch  diameter,  as  drawn 

Same,  annealed 

Wire  y\  to  -^^  inch  diameter,  as  drawn 

Wire  ^  to  ^ J ^  inch  diameter,  as  drawn 

Same,  annealed 

Plates  to  \  inch  thick,  as  rolled 

Same,  annealed 

Sheets  \  to  -^-^  inch  thick,  as  rolled 

Same,  annealed 

Sheets  ^V  '°  ttss  '^^'^  'C!\\<^,  as  rolled 

Same,  annealed 

•a  3  § 












»H  4)    u 

■a  p-.s 

rt  ^    rt 












•a    . 

&    O 

a  a 

4)  j-j  • 

"S  ">  So 





















Compressive  Tests. 

Same  metal  is  in  above  tensile 
tests,  about  98  per  cent.  pure. 

Ordinary  casting,  as  cast 

Same,  annealed 

Same,  hardened  by  drop  forging. 

Rolled  bars,  left  hard 

Same,  annealed 

Hammered  bars,  left  hard 

Same,  annealed 

Metal  containing  4.5  per  cent, 
silicon  and  1.5  per  cent,  iron, 
casting,  unannealed 

Metal  containing  1.14  per  cent, 
silicon  and  0.05  per  cent,  iron, 
castings,  unannealed 

Same,  larger  test-piece 


DA  . 



•=  0.  c 

"»-S  a 

e  »■" 


0,  a  <u 

n  po 

^^ .«  (fl 























'u  a 

Height  X  diam. 

I  in.  X  0.5  in. 
I  in.  X  0.5  in. 
I     in.  X  0.5    in. 

1.5  in.  X  0.75  in. 
1.5  in.  X  0.75  in. 

m.  XI.5    m. 
in.  X  1.5    in. 

I     m.  X0.5    m. 

I     in.xo.5    in. 
3     in.  X  1.5    in. 

Height  X  diam. 

0.985  X  0.503 
0.975  *  0.506 
0.965  X  0.508 


2.91  X  1.520 
2.91    X  1.519 

0.965  X  0.508 

0.975  X  0-507 

2.92    X  1.519 

Transverse  Tests. 

Metal  containing  98.52  per  cent,  aluminium, 
1. 14  per  cent,  silicon,  and  0.05  per  cent.  iron. 

Test-piece  one  inch  square,  supported  on  knife 
edges  24  inches  apart,  loaded  in  the  centre . . . 

Same  metal,  test-piece  a  1.5  inch  diameter  rolled 
bar,  on  knife-edges  12  inches  apart,  loaded  in 
the  centre 






set,  inches. 
















































From  the   various  tests   above  enumerated,  Messrs.  Hunt,. 
Langley  and  Hall  draw  the  following  general  conclusions : 

The  average  strength  of  commercial  aluminium  of  the  follow 
ing  average  composition : 

Aluminium 97.      to  99.    per  cent. 

Graphitic  silicon o.i    to    i.o      " 

Combined     "      0.9    to    2.8       " 

Iron 0.04  to    0.2       " 

is  as  follows : 

Elastic  limit  in  tension. 

i-  Castings. 

Sheet  . . . 

I  Bars 

Pounds  per  square  inch. 



16,000-30,000  (according  to  fineness)' 


Ultimate  strength  in  ten- 

30,000-65,000  (according  to  fineness) 

Percentage    of    reduction 

Castings  . 


iction  j 
of  area,  in  tension  ....    ]   Wire 
L  Bars. 

15  per  cent.. 

35  " 
60  " 
40       " 


Elastic  limit  in  compression  in  cylinders  with  length  twice  the  diameter 3,50o 

Ultimate  strength ■ 12,000 

Modulus  of  elasticity,  castings 1 1,000,000 

"  "  cold-drawn  wire 19,000,000 

"  "  sheets  and  bars 13,000,000 

Professor  Le  Chatelier  *  has  shown  that  the  tensile  strength 
of  annealed  aluminium  wire  varies  with  the  temperature  as 
follows : 

Kilos  per  sq.  millimetre.  Pounds  per  sq.  inch. 

At     0°  C.  1 8  26,000 

150°  13  18,500 

250°  7  1 0,000 

300°  5  7^000 

40o<^  2  3,000 

*  Lejeal's  Aluminium. 


Minet  found  the  following  properties  for  aluminium  strongly 
worked  and  annealed : 

Tensile  strength.  Elongation. 
Kilos  per  sq.  mm.        Pounds  per  sq.  in.      Per  cent. 

After  working 23.5  33iOOO  3 

After  being  annealed  I  hour  at  400° 15.1  21,500  17 

He  concludes  from  these  results  that,  by  careful  annealing  at 
proportionate  temperatures  and  for  proportionate  times,  any 
given  strength  between  these  limits  may  be  obtained,  or  any 
■desired  elasticity  from  3  to  17  per  cent. 

The  results  obtained  for  the  tensile  strength  of  aluminium 
show,  in  general,  that  it  is  greatly  influenced  by  the  amount  of 
work  done  on  the  metal ;  that  while  the  pure,  unworked  metal 
is  by  no  means  rigid,  but  elongates  10  to  20  per  cent,  before 
breaking,  as  it  is  worked  it  becomes  stififer  and  more  elastic,  its 
strength  may  be  nearly  doubled,  but  it  becomes  at  the  same 
time  more  brittle,  as  is  shown  by  its  elongation  falling  to  3  or  5 
per  cent.  After  working,  increased  elongation  can  be  given  to 
it  by  annealing,  but  at  the  expense  of  ultimate  strength.  The 
annealed  material,  however,  would  be  a  safer  rhaterial  to  use  in 
any  place  where  sudden  shocks  had  to  be  sustained,  if  worked 
within  its  elastic  limit. 

Taking  the  tensile  strength  of  aluminium  in  relation  to  its 
weight,  it  shows  a  very  high  mechanical  value ;  in  fact,  the  only 
material  which  can  compare  with  it  in  tensile  strength,  weight 
for  weight,  is  the  finest  steel  or  aluminium  bronze.  A  com- 
parison on  this  basis  is  frequently  made,  in  order  to  determine 
the  material  which  gives  the  greatest  strength  for  a  given 
weight,  or,  rather,  a  given  strength  with  the  least  weight.  For 
instance,  we  might  make  the  comparison  by  calculating  the 
weight  of  rods  of  the  different  metals  which  would  support  a 
certain  maximum  strain  before  breaking,  and  from  these  num- 
bers derive  a  table  of  the  relative  weights  of  the  metals  to  give 
a  certain  strength : 


Tensile  strength,  Relative  strength  Relative  strength 

Rolled  Bars  or  Large  Wire.        pounds  per  sq.  in.  for  same  section,  for  same  weight. 

Aluminium   30,000  100                       100 

Cast  steel 100,000  333                      135 

Soft  steel 75,000  250                       87 

Wrought  iron S5,oco  183                       63 

Aluminium  bronze  .......        100,000  333                       118 

"           brass 60,000  200                       70 

Gun  bronze 35,000  117                       37 

Red  brass 45,000  150                       47 

Copper 33,000  1 10                       33 

It  results  from  this  comparison  that  only  steel  of  the  highest 
quality  and  the  best  aluminium  bronze  will  give  a  greater 
strength  for  a  given  weight  than  aluminium.  Steel,  however, 
is  subject  to  rust,  whereas  aluminium  is  not ;  aluminium  bronze 
itself  is  a  metal  requiring  considerable  skill  in  working  it  to 
always  obtain  the  highest  results ;  these  two  are  the  only  com- 
petitors which  aluminium  has  for  constructions  where  great 
strength  combined  with  lightness  is  the  first  requirement,  and 
expense  is  a  secondary  consideration. 


Aluminium  stands  high  in  the  list  of  malleable  metals.  It 
can  be  forged  or  rolled  as  easily  as  gold  or  silver,  and  can  be 
beaten  out  into  leaf. 

Mallet  found  that  absolutely  pure  aluminium  is  decidedly 
more  malleable  than  the  commercial  metal,  and  is  less  hardened 
by  working.  Experience  in  rolling  it  on  a  large  scale  has  since 
shown  that  the  more  impurity  in  the  metal  the  harder  it  is  to 
work,  and  the  quicker  it  will  become  hard  and  need  annealing. 
Some  impurities,  however,  are  more  detrimental  than  others. 
One  per  cent,  of  iron  renders  the  metal  stronger  and  harder  to 
roll,  but  more  than  this  amount  renders  it  less  and  less  malle- 
able, until  with  6  per. cent,  it  is  crystalline  and  brittle.  On  the 
other  hand,  silicon  may  occur  alone  up  to  nearly  10  per  cent, 
without  rendering  the  metal  unfit  for  rolling. 

Aluminium  is  most  malleable  between  100°  and  150°  C,  and 
can  be  worked  some  time  at  that  temperature  before  becoming 


hard.  If  rolled  or  worked  cold,  it  needs  more  frequent  anneal- 
ing. While  annealed  aluminium  is  one  of  the  softest  and  most 
pliable  metals,  yet  by  cold  working  it  can  be  given  the  stiffness 
and  temper  of  hard  brass.  The  best  commercial  metal  is 
regularly  rolled  into  sheets  one-thousandth  of  an  inch  in  thick- 
ness, which  sheets  are  sold  for  beating  purposes,  and  it  has 
been  rolled  to  one-half  that  thickness. 

Metal  for  beating  into  leaf  must  be  of  the  finest  quality,  i.  e., 
over  99  per  cent.  pure.  Rousseau,  of  Paris,  was  the  first  to 
make  aluminium  leaf,  and  it  was  afterwards  made  for  several 
years  by  C.  Falk  &  Co.,  of  Vienna.  At  present,  Mr.  Kemp,  of 
New  York,  manufactures  it  on  a  large  scale.  The  beating  is  a 
little  harder  than  is  required  for  gold  and  silver,  but  by  starting 
with  the  purest  aluminium  equally  thin  leaf  can  be  obtained. 
A  specimen  of  commercial  aluminium  leaf  examined  by  the 
writer  had  a  thickness  of  0.000638  millimetre,  or  one  forty- 
thousandth  of  an  inch,  which  compares  favorably  with  ordinary- 
silver  leaf.  This  leaf  was  opaque,  but  the  thinnest  attainable 
leaf  is  a  fine  blue  by  transmitted  light.  No  other  useful  metals 
except  gold  and  silver  will  show  such  malleability.  This  leaf  is 
now  in  regular  use  with  gilders  and  decorators,  and  has  en- 
tirely superseded  silver  leaf  because  of  its  cheapness  and  non- 
tarnishing  qualities.  The  leaf  is  also  rubbed  into  powder,  and 
in  that  state  used  as  a  metallic  dust  in  printing  and  decorating. 


Aluminium  can  be  drawn  into  very  fine  wire.  Even  as  early 
as  1855,  M.  Vangeois  made  very  fine  wires  with  metal  far  from 
being  pure,  and  used  them  for  making  aluminium  passementerie. 
The  metal  quickly  hardens  at  the  drawing  plate,  and  must  be 
frequently  annealed.  The  larger  sizes  of  wire  can  be  drawn 
warm,  and  then  require  less  frequent  annealing.  The  heated 
gases  from  the  chimney  of  an  Argand  burner  will  anneal  the 
very  fine  wires  if  they  are  simply  passed  across  it.  Wire  as 
fine  as  o.i  millimetre  (one  two-hundred-and-fiftieth  of  an  inch) 
can  be  made  without  much  trouble,  while  wire  one-seventieth 


of  an  inch  in  diameter  is  regularly  kept  in  stock  by  the  alu- 
minium dealers. 

Gold,  silver,  platinum,  iron  and  copper  are  probably  the  only 
metals  more  ductile  than  aluminium. 

Expansion  by  Heat. 

Fizeau  determined  that  aluminium  expands  0.00222  of  its 
length  in  passing  from  the  freezing  point  to  the  boiling  point, 
or  0.0000222  of  its  length  for  a  rise  of  1°  Centigrade,  equal  to 
O.OOOOI129  per  1°  Fahrenheit. 

Prof.  J.  W.  Langley  examined  metal  98.5  per  cent,  pure,  the 
rest  being  mostly  silicon,  and  obtained  for  the  expansion  for 
1°  C.  0.0000206,  which  would  be  o.ooooi  15  for  1°  F. 

A  bar  of  aluminium  i  foot  long  at  0°  C.  would,  according  to 
Fizeau,  be  1.00222  feet  long  at  100°,  while  a  cubic  foot  of 
aluminium  at  0°  would  occupy  1.00666  cubic  feet  at  100°  C, 
since  the  rate  of  cubical  increase  is  three  times  that  of  linear 
expansion.  This  rate  of  expansion  is  close  to  that  of  tin, 
among  the  common  metals. 

Specific  Heat.* 

The  best  experimenters  have  given  various  values  for  the 
specific  heat  of  aluminium,  but  it  is  very  evident  to  the  writer 
that  the  differences  are  mainly  due  to  differences  in  the  purity 
of  the  metal  used.  Professor  Mallet  used  absolutely  pure  alu- 
minium (purified  for  atomic  weight  determination),  and  the 
writer  used  metal  which  analyzed  99.93  per  cent,  pure,  and  con- 
tained but  a  trace  of  iron,  while  the  other  experimenters  used 
■ordinary  commercial  metal  made  by  the  sodium  process  and 
■containing  considerable  quantities  of  iron. 

Regnault,  in  1855,  used  metal  containing  only  88.35  percent, 
of  aluminium.  His  figure  of  0.2056,  between  25°  and  97°,  is, 
therefore,  only  approximate. 

*  For  further  details,  see  papers  on  this  subject  by  the  author  in  Journal  of  the 
franklin  Institute,  April,  1892,  and  July,  1893. 


In  1856,  Regnault  obtained  metal  97  per  cent,  pure,  with 
which  he  obtained  O.2122  (14°  to  97°). 

Kopp,  in  1863,  used  Parisian  aluminium  containing  two  per 
cent,  of  iron,  and  obtained  a  value  varying  between  O.1970  and 
0.2070  (20°  to  52°).     His  results  are  unreliable. 

In  1882,  Mallet  found  the  mean  specific  heat  from  0°  to  100°, 
using  absolutely  pure  aluminium,  0.2253. 

Tomlinson  *  used  commercial  aluminium  in  wire,  and  gives 
the  following  formula  for  the  mean  specific  heat,  from  any 
given  temperature  to  0°  C. : 

Sm  =  0.2070  4"  O.OOOI  151. 

This  would  give  from  0°  to  100°,  0.2185. 
Naccari  f  used  commercial  metal,  and  gives  the  following  for- 
mula, which  expresses  his  results  up  to  300°  C. : 

Sm  =  0.2116  +  0.0000475  *• 

This  would  give  from  0°  to  100°,  0.2 164. 

Le  VerrierJ  stated  that  he  found,  using  best  commercial 
metal,  the  specific  heat  between  0°  and  300°  to  be  invariable, 
and  =  0.22  ;  between  300°  and  530°  also  constant,  and  =  0.30; 
between  530°  and  560°  an  absorption  of  heat,  rendered  latent, 
of  about  10  calories;  between  540°  and  600°  the  specific  heat 
again  constant,  and  =  0.46.  For  the  total  quantities  of  heat 
in  the  metal,  at  various  temperatures,  he  gives : 

o''  to  300°  Q  =  0.22  t. 

300°  to  530°  Q  =     65  +  0.30  (t— 300). 

540°  to  600°  Q  =   139  -\-  0.46  (t — 530). 

About    600°  Q  =   170. 

Before  fusion  at  620°  Q  =   200. 

These  determinations  would  give  the  mean  specific  heat 
from  0°  to  100°,  0.2200.  No  other  investigator,  however,  has 
noticed  the  sudden  jumps  noted  by  Le  Verrier,  which,  if  true, 

*Proc.  Royal  Society,  1885,  p.  494. 

t  Trans.  Accademia  di  Torino,  Dec,  1887. 

I  Comptes  Rendus,  1892,  Vol.  114,  p.  907. 


are  indeed  very  singular.  Experiments  by  Pionchon  and  the 
writer,  about  to  be  described,  gave  no  indications  of  such  criti- 
cal points. 

Pionchon*  states  that  he  used  very  pure  aluminium,  and  ob- 
tained the  following  formulae : 

291-86  t 
0°  to  580°  Q  =  0.393  t-  giy.8  4- 1 

625°  to  800°  Q  =  0.308  t— 46.9. 


This  would  give  the  specific  heat  at  0°,  =  0.2010;  the 
mean  specific  heat  0°  to  100°  =  0.2 130;  heat  in  solid  alu- 
minium at  its  melting-point,  160.5  calories;  heat  in  molten 
aluminium  at  the  setting-point,  239.4  calories ;  specific  heat  of 
molten  aluminium  constant,  and  =  0.308.  The  latent  heat  of 
fusion  would  be  239.4 —  160.5  =  7^-9  calories. 

The  writer,  using  aluminium  which  analyzed  99.93  per  cent, 
pure,  with  only  a  trace  of  iron  and  0.07  per  cent,  silicon,  ob- 
tained the  following  formulae  for  solid  aluminium  up  to  600° : 

Mean  specific  heat  to  o°-  Sm  =  0.2220   -|-  0.00005  t. 

True  specific  heat  at    t°-  S     =  0.2220   -\-  o.ocoi  t. 

Total  heat  to  o°-  Q   =  0.2220 1  -|-  0.00005  t'. 

These  formulae  give  for  the  specific  heat  at  0°  =0.2220; 
the  mean  specific  heat  0°  to  100°  =  0.2270;  the  heat  in  solid 
aluminium  at  the  melting-point,  158.3  calories;  specific  heat  at 
the  melting-point,  0.285. 

Regarding  these  figures,  it  will  be  observed  that  the  mean 
value  0°  to  100°  is  less  than  i  per  cent,  different  from  Mallet's 
result,  and  therefore  these  values  may  be  accepted  as  the  true 
value  of  the  mean  specific  heat  between  those  temperatures. 
Regarding  the  value  for  the  heat  contained  at  the  melting-point, 
it  is  only  a  fraction  over  i  per  cent,  removed  from  that  given 
by  Pionchon's  formula.  It  must  not  be  forgotten,  however, 
that  aluminium  begins  to  soften  at  about  600°,  and  some  of  its 
latent  heat  of  fusion  is  absorbed  before  the  true  melting-point, 

*Comptes  Rendus,  1892,  Vol.  115,  p.  163. 


625°,  is  reached,  as  observed  by  both  Pionchon  and  Le  Verrier. 
The  numbers  given  by  the  formulae  are  the  theoretical  amounts 
of  heat  which  the  metal  would  contain  at  625°,  provided  that 
none  of  the  latent  heat  of  fusion  had  been  previously  absorbed. 
To  determine  the  amount  of  heat  in  the  molten  metal  at  its 
setting  point  the  writer  made  several  determinations  by  pour- 
ing the  metal  into  water,  just  as  it  was  setting.  The  result 
showed  that  the  purity  of  the  metal  had  a  great  effect  on  the 
amount  of  heat  thus  given  up. 

Aluminium  96.9  per  cent,  pure  gave  up 229.0  calories. 

99-9       "  "  "     254-0       " 

99-93     "  "  "     258.3       " 

It  is  seen  that  a  small  amount  of  impurity  makes  a  large 
difference,  which  is  really  caused  by  the  impurity  lowering  the 
melting  point  of  the  metal.  Since  the  metal  used  by  Pionchon 
was  not  over  99.7  per  cent,  pure,  we  have  a  partial  explanation 
of  why  he  obtained  only  239.4  calories  in  the  molten  metal. 
The  figure  deduced  by  the  writer  for  the  latent  heat  of  fusion 
of  aluminium  is  therefore  258.3 — 158.3=100  calories. 

The  value  of  the  specific  heat  of  aluminium  determined  by 
Mallet  and  the  writer  agrees  best  with  Dulong  and  Petit's  law, 
as  is  seen  by  the  following  comparison  of  the  actual  and  atomic 
specific  heats  for  the  interval  0°  to  100°  : 

Experimenter.                                            Specific  Heat  x  Atomic  Weight=  Atomic  Heat. 
Regnault 0.2122      x       27.0        =        5.73 

Kopp   0.2020 

Tomlinson 0.2185 

Naccari 0.2164 

Le  Verrier 0.2200 

Pionchon 0.21 30 

Mallet 0.2253 

Richards .  0.2270 



Since  for  all  the  common  metals  the  product  of  the  atomic 
weight  by  the  specific  heat  for  this  range  of  temperature  is  in- 
variably above  6.0,  and  averages  6.2,  the  conclusion  is  plain 
that  the  last  two  figures  given  above  must  be  the  correct  ones. 


The  high  value  of  the  specific  heat  of  aluminium  compared 
with  other  metals,  and  particularly  its  large  latent  heat  of 
fusion,  cause  the  metal  to  melt  very  slowly  even  in  a  very  hot 
fire.  As  seen  above,  over  258  calories  have  to  be  absorbed 
in  order  to  raise  it  to  the  melting  point  and  melt  it.  It  com- 
pares with  other  metals  as  follows : 

Aluminium 25^-3  calories. 

Cast  iron  250.0        " 

Copper    162.0        " 

Platinum 102.4        " 

Silver 85.0 

Gold    58.0        " 

We  can  therefore  deduce  the  interesting  fact,  which  is  amply 
confirmed  by  observation,  that  having  a  furnace  hot  enough  to 
melt  cast  iron,  we  would  find  that  a  given  weight  of  gold,  silver 
or  copper  would  melt  before  the  same  weight  of  aluminium, 
and  even  the  cast-iron  would  not  be  far  from  melting  by  the 
time  the  aluminium  fused. 

Electric  Conductivity. 

Aluminium  is  a  very  good  conductor  of  electricity.  Metal 
used  for  electrical  purposes  should  be  of  the  best  quality,  and  as 
free  as  possible  from  intermingled  slag  or  blow-holes,  which 
impair  greatly  its  conductivity. 

Taking  the  electrical  conductivity  of  absolutely  pure  silver  or 
copper  as  100,  we  cite  the  following  determinations  : 

Silver  =  100.      Copper  =  100. 

Mattheissen.     Commercial  aluminium 33-76 

Benoit.     Annealed  wire 49-7° 

Watts 5610 

*Lorenz 49.1  at      0°. 

■<        50.1  at  100°. 

'■  Unnealed  wire 54.8  at    14°. 

"     53-7  at    76°. 

Annealed     "     S7.4  at    14°. 

"          "     SS-9  at    76°. 

Weiler.     Best  commercial  metal S4-20                54.3 

tC.  K.  McGee.     Metal  used 
98.52  per  cent.  pure. 

*  Wied.  Annalen,  |  2],  xiii,  422,  582  (1881). 
t  Trans.  Am.  Inst.  Mining  Engineers,  xviii,  528  (1890). 


The  later  determinations  of  McGee  and  Weiler  agree  very 
satisfactorily.  Taking  54.8  as  the  relative  resistance  at  ordinary 
temperatures,  a  wire  of  aluminium  o.i  inch  in  diameter  and  lOO 
feet  long  would  have  a  resistance  of  0.20235  ohms. 

Professor  Dewar  has  recently  investigated  the  electrical  re- 
sistance of  the  metals  at  very  low  temperatures.  He  finds  with 
aluminium,  as  with  other  metals,  that  the  resistance  varies 
directly  as  the  absolute  temperature.  The  following  are  his 
results : 

Relative  Electrical  Resistances. 

Temperature,       Pure  Silver.        Pure  Copper.  Aluminium. 

C°  ....  ....       99  per  cent.  97.5  per  cent. 

ig.i  1588  1682  2772  2869 

i.o  2583  2683 

—82  1704  1738 

—197  ....  ....  560  506 

—219  ....  ....  ....  325 

Thermal  Conductivity. 

Faraday  stated  that  he  had  found  by  a  very  simple  experi- 
ment that  aluminium  conducted  heat  better  than  either  silver 
or  copper. 

L.  Lorenz  of  Copenhagen,  in  the  Jahresbericht  der  Chemie, 
1881,  p.  94,  stated  that  he  had  found  it  inferior  to  both  of  these 
metals,  and  later  investigations  have  confirmed  this. 

Professor  Carhart,  of  the  University  of  Michigan,  finds  that 
annealed  aluminium  is  a  slightly  better  heat  conductor  than 
the  unannealed. 

The  various  results  are  as  follows : 

Silver  =  100,  Copper  =  loo. 

L.  Lorenz 47-72  at      0°. 

L.  Lorenz ; .  50.00  at  100°. 

Calvert  and  Johnson 66.5 

Prof.  Carhart.     Annealed  Metal 38.87  52.8 

Prof.  Carhart.    Unannealed  Metal 37-96  51.6 

Gold  is  the  only  other  metal  which  conducts  heat  better  than 



We  would  here  repeat  the  remark  made  with  regard  to  the 
physical  properties,  that  the  properties  to  be  recorded  are  those 
of  the  purest  metal  unless  specifically  stated  otherwise.  How- 
ever, the  high  grade  of  commercial  metal  differs  very  little  in 
most  of  its  chemical  properties  from  the  absolutely  pure,  so 
that  not  many  reservations  are  necessary  in  applying  the  fol- 
lowing properties  to  good,  commercial  metal: 

Atomic  Weight. 

The  most  accurate  determination  which  we  have  is  that  of 
Professor  Mallet,  who  found  27.02.  For  all  practical  purposes, 
and  even  in  analyses,  it  may  be  conveniently  considered  as  27. 
The  chemical  equivalent  weight  is  one-third  of  this,  or  9. 

Action  of  Air. 

Deville:  "Air,  wet  or  dry,  has  absolutely  no  action  on  alu- 
minium. No  observation  which  has  come  to  my  knowledge 
is  contrary  to  this  assertion,  which  may  easily  be  proved  by 
any  one.  I  have  known  of  beams  of  balances,  weights,  plaques, 
polished  leaf,  reflectors,  etc.,  of  the  metal  exposed  for  months 
to  moist  air  and  sulphur  vapors  and  showing  no  traoe  of  alter- 
ation. We  know  that  aluminium  may  be  melted  in  the  air  with 
impunity,  therefore  air  and  also  oxygen  cannot  sensibly  afifect 
it.  It  resisted  oxidation  in  the  air  at  the  highest  heat  I  could 
produce  in  a  cupel  furnace,  a  heat  much  higher  than  that  re- 
quired for  the  assay  of  gold.  This  experiment  is  interesting, 
especially  when  the  metallic  button  is  covered  with  a  layer  of 
oxide  which  tarnishes  it,  the  expansion  of  the  metal  causing 



small  branches  to  shoot  from  its  surface,  which  are  very  bril- 
liant and  do  not  lose  their  lustre  in  spite  of  the  oxidizing  at- 
mosphere. M.  Wohler  has  also  observed  this  property  on  try- 
ing to  melt  the  metal  with  a  blowpipe.  M.  Peligot  has  profited 
by  it  to  cupel  aluminium.  I  have  seen  buttons  of  impure 
metal  cupelled  with  lead  and  become  very  malleable. 

"With  pure  aluminium  the  resistance  of  the  metal  to  direct 
oxidation  is  so  considerable  that  at  the  melting  point  of  plati- 
num it  is  hardly  appreciably  touched,  and  does  not  lose  its 
lustre.  It  is  well  known  that  the  more  oxidizable  metals  take 
this  property  away  from  it.  But  silicon  itself,  which  is  much 
less  oxidizable,  when  alloyed  with  it  makes  it  burn  with  great 
brilliancy,  because  there  is  formed  a  silicate  of  aluminium." 

While  the  above  observations  are  in  the  main  true,  yet  it  is 
now  well  known  that  objects  made  of  commercial  aluminium  do 
after  a  long  exposure  become  coated  with  a  very  thin  film,  which 
gives  the  surface  a  "dead"  appearance.  The  coating  is  very 
similar  in  appearance  to  that  forming  on  zinc  under  the  same 
circumstances.  The  oxidation,  however,  does  not  continue,  for 
the  film  seems  to  be  absolutely  cdntinous  and  to  protect  the 
metal  underneath  from  further  oxidation.  This  coating  can  best 
be  removed  by  very  dilute  acid  (see  Mourey's  receipt,  p.  6o), 
after  which  the  surface  can  be  burnished  to  its  former  brilliancy. 

The  action  of  air  and  rain  water  together  also  slightly  cor- 
rodes commercial  aluminium,  the  sheet  metal  particularly 
showing  after  several  months  exposure  small  white  spots  of 
alumina  wherever  there  was  a  speck  or  "  piqfire."  In  no  case, 
however,  is  this  corrosion  very  strong  or  anything  like  as 
serious  as  the  rusting  of  iron  or  corrosion  of  brass,  copper,  etc. 

It  has  also  been  found  that  at  a  high  white-heat,  especially 
at  the  heat  of  an  electric  furnace,  aluminium  burns  with  a  strong 
light  to  alumina.  It  is  quite  probable  that  in  this  case  it 
volatizes  first,  and  it  is  the  vapor  which  burns.  During  the 
operation  of  an  electric  furnace  a  white  smoke  formed  of  invisi- 
ble particles  of  alumina  is  thus  formed  and  evolved  from  the 
furnace.     Also,  in  melting  aluminium,  even  the  purest,  it  will 


be  found  that  the  surface  seems  bound  and  the  aluminium 
restrained  from  flowing  freely  by  a  minute  "  sl^in  "  which  may 
probably  be  a  mixture  of  oxide  with  metal,  or  perhaps  of  oxides 
of  foreign  metals ;  but,  nevertheless,  it  is  always  present  and  is 
therefore  indicative  of  oxidation  taking  place.  It  seems  to  pro- 
tect the  metal  beneath  it  perfectly,  so  that,  once  formed,  it  gets 
no  thicker  by  continued  heating. 

Wohler  first  discovered  that  when  aluminium  was  in  the  ex- 
tremely attenuated  form  of  a  leaf  it  would  burn  brightly  in  air, 
and  burn  in  oxygen  with  a  brilliant  bluish-light.  It  is  also  said 
that  thin  foil  will  burn  in  oxygen,  being  heated  by  wrapping  it 
around  a  splinter  of  wood,  and  fine  wire  also  burns  like  iron 
wire,  but  the  combustion  is  not  continuous,  because  the  wire 
fuses  too  quickly.  The  alumina  resulting  is  quite  insoluble  in 
acids,  and  as  hard  as  corundum. 

The  aluminium  powder,  produced  by  pulverizing  aluminium 
leaf,  burns  brilliantly  when  projected  into  a  flame,  and  has  dis- 
placed, to  a  large  extent,  magnesium  powder  for  making  a  flash 
Hght,  because  it  is  cheaper,  gives  a  more  strongly  actinic  light, 
and  leaves  no  unpleasant  smoke  or  fumes.  For  this  purpose  it 
is  not  used  pure,  but  mixed  with  various  chemicals,  for  the 
composition  of  which  see  the  chapter  on  "Uses  of  Aluminium." 

Action  of  Water. 

Deville :  "  Water  has  no  action  on  aluminium,  either  at  ordi- 
nary temperatures  or  at  100°,  or  at  a  red  heat  bordering  on  the 
fusing  point  of  the  metal.  I  boiled  a  fine  wire  in  water  for  half 
an  hour  and  it  lost  not  a  particle  in  weight.  The  same  wire  was 
put  in  a  glass-tube  heated  to  redness  by  an  alcohol  lamp  and 
traversed  by  a  current  of  steam,  but  after  several  hours  it  had 
not  lost  its  polish,  and  had  the  same  weight.  To  obtain  any 
sensible  action  it  is  necessary  to  operate  at  the  highest  heat  of 
a  reverberatory  furnace — a  white  heat.  Even  then  the  oxida- 
tion is  so  feeble  that  it  develops  only  in  spots,  producing  almost 
inappreciable  quantities  of  alumina.  This  slight  alteration  and 
■the  analogies  of  the  metal  allow  us  to  admit  that  it  decomposes 


water,  but  very  feebly.  If,  however,  metal  produced  by  M. 
Rose's  method  is  used,  which  is  almost  unavoidably  contam- 
inated with  slag  composed  of  chlorides  of  aluminium  and 
sodium,  the  former,  in  presence  of  water,  plays  the  part  of  an 
acid  towards  aluminium,  disengaging  hydrogen  with  the  forma- 
tion of  a  subchlorhydrate  of  alumina,  whose  composition  is  not 
known,  and  which  is  soluble  in  water.  When  the  metal  thus 
tarnishes  in  water  one  may  be  sure  to  find  chlorine  in  the  water 
on  testing  it  with  nitrate  of  silver." 

Aluminium  leaf,  however,  will  slowly  decompose  water  at 
ioo°.  Hydrogen  is  slowly  evolved,  the  leaf  loses  its  brilliancy, 
becomes  discolored,  and,  after  some  hours,  translucent.  It  is 
eventually  entirely  converted  into  gelatinous  hydrated  alumina. 

A.  Ditte  *  explains  the  action  of  water  on  aluminium  as  fol- 
lows :  Water  can  only  act  on  aluminium  by  producing  hydro- 
gen gas  and  alumina,  both  of  which  deposit  on  the  metal  and 
cover  it  with  a  thin,  protective  coating.  If  the  conditions  are 
such  that  this  coating  is  removed,  the  action  becomes  manifest. 
Boiling,  for  instance,  removes  the  hydrogen,  and  if  chloride, 
sulphate  or  nitrate  of  aluminium  be  present  in  the  solution  to 
remove  the  alumina,  the  action  goes  on,  a  basic  salt  being 
formed,  and  continues  until  a  sub-salt  is  formed  which  is  diffi- 
cultly soluble  or  insoluble,  and  covers  the  metal  with  a  new, 
impermeable  coating.  Traces  of  these  acids  in  the  boiling 
water  would  lead  to  the  same  result. 

Action  of  Hydrogen  Sulphide  and  Sulphur. 

Deville :  "  Sulphuretted  hydrogen  exercises  no  action  on 
aluminium,  as  may  be  proved  by  leaving  the  metal  in  an 
aqueous  solution  of  the  gas.  In  these  circumstances  almost  all 
the  metals,  and  especially  silver,  blacken  with  great  rapidity. 
Sulph-hydrate  of  ammonia  may  be  evaporated  on  an  alumin- 
ium leaf,  leaving  on  the  metal  only  a  deposit  of  sulphur,  which 
the  least  heat  drives  away. 

*  Ann.  de  Chimie  et  de  Physique  [6],  Vol.  20,  p.  404  (i8go). 


"  Aluminium  may  be  heated  in  a  glass  tube  to  a  red  heat  in 
vapor  of  sulphur  without  altering  the  metal.  This  resistance  is 
such  that  in  melting  together  polysulphide  of  potassium  and 
some  aluminium  containing  copper  or  iron,  the  latter  are  at- 
tacked without  the  aluminium  being  sensibly  affected.  Un- 
happily, this  method  of  purification  may  not  be  employed 
because  of  the  protection  which  aluminium  exercises  over 
foreign  metals.  Under  the  same  circumstances  gold  and  silver 
dissolve  up  very  rapidly.  However,  at  a  high  temperature  I 
have  observed  that  ,it  combines  directly  with  sulphur  to  give 
aluminium  sulphide.  These  properties  varying  so  much  with 
the  temperafure  from  one  of  the  special  characteristics  of  the 
metal  and  its  alloys." 

Margottet  states  that  hydrogen  sulphide  is  without  action  on 
aluminium,  as  also  are  the  sulphides  of  iron,  copper,  or  zinc. 
Aluminium  is  said  to  decompose  silver  sulphide,  AgjS,  setting 
the  sulphur,  however,  at  liberty,  and  alloying  with  the  silver. 
In  regard  to  its  indifference  to  the  first  mentioned  sulphides, 
this  would  give  inferential  evidence  that  the  reverse  operation, 
i.  e.,  the  action  of  iron,  copper,  or  zinc  on  aluminium  sulphide, 
would  be  possible,  as  will  be  seen  later  to  be  apparently 
established  by  direct  experiment.  As  to  the  action  of  sul- 
phuretted hydrogen,  the  author  has  a  different  experience  to 
quote.  On  passing  a  stream  of  that  gas  into  commercial  alu- 
minium melted  at  a  red  heat,  little  explosive  puffs  were  heard, 
accompanied  by  a  yellow  light,  while  the  dross  formed  on  the 
surface,  when  cooled,  evolved  sulphuretted  hydrogen  briskly 
when  dropped  into  water,  and  gave  every  indication  of  contain- 
ing aluminium  sulphide.  It  could  not  have  been  silicon  sul- 
phide, for  the  metal  contained  as  large  a  percentage  of  silicon 
after  treatment  as  before.  Hydrogen  sulphide  is  also  absorbed 
in  large  quantity  by  molten  aluminium,  and  mostly  evolved  just 
as  the  metal  is  about  to  set.  Some  of  the  gas  is  entangled  in 
the  solidifying  metal,  forming  and  fiUing  numerous  cavities  or 

88  aluminium. 

Sulphuric  Acid. 

Deville :  "  Sulphuric  acid,  diluted  in  the  proportion  most 
suitable  for  attacking  the  metals  which  decompose  water,  has 
no  action  on  aluminium  ;  and  contact  with  a  foreign  metal  does 
not  help,  as  with  zinc,  the  solution  of  the  metal,  according  to 
M.  de  la  Rive.  This  singular  fact  tends  to  remove  aluminium 
considerably  from  those  metals.  To  establish  it  better,  I  left 
for  several  months  some  globules  weighing  only  a  few  milli- 
grammes in  contact  with  the  weak  acid,  and  they  showed  no 
visible  alteration ;  however,  the  acid  gave  a  faint  precipitate 
when  neutralized  with  aqua  ammonia." 

It  is  a  fact  that  dilute  or  concentrated  sulphuric  acid  acts 
very  feebly  on  pure  aluminium  in  the  cold,  but  on  being  heated 
they  both  attack  it,  disengaging  sulphurous  acid  gas.  Impure 
metal  is  attacked  more  easily  than  pure  metal,  the  presence  of 
silicon  giving  rise  to  the  formation  of  silicon  hydride,  which 
communicates  to  the  hydrogen  set  free  a  tainted  odor. 

Ditte*  describes  the  action  of  sulphuric  acid  as  follows :  A 
2.5  per  cent,  solution  acts  very  slowly  at  first,  if  cold,  but  after 
several  hours  the  air  condensed  on  the  aluminium  is  removed 
and  the  metal  is  slowly  dissolved,  evolving  hydrogen.  The 
bubbles  of  hydrogen,  however,  protect  the  surface  from  further 
attack,  but  anything  which  breaks  up  or  removes  this  gaseous 
envelope  hastens  the  action  of  the  acid.  Certain  solutions  of 
metallic  chlorides  which  aluminium  reduces  act  in  this  way. 
If,  for  instance,  we  add  a  few  drops  of  platinic  chloride  to  the 
above  acid,  platinum  is  reduced  on  the  aluminium,  the  surface 
is  roughened,  causing  the  gas  to  escape  quicker,  and  the  action 
is  much  more  rapid.  Traces  of  chloride  of  gold,  mercury  or 
copper  have  the  same  effect.  After  some  time,  the  action  of 
the  acid  is  stopped  by  the  formation  of  an  insoluble  basic  salt, 
having  the  formula  4AI2O3.3SO3.18H2O,  which  deposits  on  the 
metal  and  protects  it  from  further  action.  Even  very  dilute 
sulphuric  acid  attacks  aluminium  if  it  is  prevented  from  cover- 
ing itself  with  the  layer  of  gas,  as  by  boiling. 

♦Comptes  Rendus,  ex.,  pp.  583,  782  (1890). 














It  appears  to  the  writer  that  similar  reasoning  explains  why 
impure  aluminium  is  attacked  more  rapidly.  Aluminium  being 
electro-positive  towards  the  impurities  it  contains,  it  follows 
that  when  the  aluminium  is  at  all  attacked  by  the  acid  the  gas 
will  be  disengaged  on  the  particles  of  the  impurity,  and  not  on 
the  aluminium  itself ;  thus  the  pure  aluminium  will  never  get 
the  benefit  of  the  gaseous  protection,  and  the  action  proceeds 

G.  A.  Le  Roy*  tested  four  specimens  of  commercial  alu- 
minium, whose  analysis  was  as  follows  : 


Aluminium 98.28 

Iron 1 .5o 

Silicon o.  1 2 

Specimens  A  and  B  were  made  by  the  sodium  process  at 
Nanterre ;  C  and  D  by  another  process,  not  named.  The  metal 
was  in  sheets  and  was  cut  to  a  definite  size,  cleaned  in  soda, 
washed  in  alcohol,  dried,  weighed,  and  then  put  in  the  acid. 
Afterwards  they  were  withdrawn,  washed  with  water,  dipped  in 
alcohol,  dried  and  weighed.  The  results  are  expressed  as  the 
weight  in  grammes  dissolved  during  twelve  hours  from  a  sur- 
face of  one  square  metre  : 

Quality  of  Acid.    Gravity. 

Pure    1.842 

Commercial i  .842 

Pure    1. 711 

Commercial 1. 711 

Pure    1.580 

Pure    1.263 

Pure    1.842 

Commercial i  .842 

From  these  tests  Le  Roy  concludes  that  it  is  impracticable 
to  think  of  using  aluminium  for  the  different  apparatus,  such  as 
pans,  pumps,  tank  linings,  etc.,  used  in  the  manufacture  or 
handling  of  sulphuric  acid. 

*  Le  Moniteur  Industriel,  Oct.  29,  1891. 



Loss in  grammes  per  square  metre  in  t2  hours^ 



































..   .. 
















While  these  tests  show  that  the  aluminium  is  certainly  dis- 
solved, yet  they  also  prove  that  the  action  is  very  slow.  If 
these  acids,  for  instance,  were  contained  in  an  aluminium  vessel 
I  millimetre  in  thickness  (0.04  inch),  we  can  easily  calculate 
from  the  above  figures  that  the  concentrated  acid  could  rest  in 
it  cold  from  60  to  90  days  before  eating  through ;  the  30°  acid, 
which  is  yet  strong,  would  take  290  to  560  days  to  get  through 
it;  while  even  the  hot  concentrated  acid  would  not  get  through 
in  less  than  5  days'  constant  action.  We  can  infer  that  cold, 
dilute  acid  would  probably  take  several  years  in  producing  the 
same  efTect. 

Nitric  Acid. 

Deville  :  "  Nitric  acid,  weak  or  concentrated,  does  not  act  on 
aluminium  at  the  ordinary  temperature.  In  boiling  acid,  solu- 
tion takes  place,  but  with  such  slowness  that  I  had  to  give  up 
this  mode  of  dissolving  the  metal  in  my  analyses.  By  cooling 
the  solution  all  action  ceases.  On  account  of  this  property, 
M.  Hulot  has  obtained  good  results  on  substituting  aluminium 
for  platinum  in  the  Grove  battery." 

Ditte*  describes  the  action  of  nitric  acid  similarly  to  that 
of  sulphuric.  Cold  3  per  cent,  acid  acts  very  slowly,  6 
per  cent,  quicker  but  slower  than  sulphuric  acid  of  the 
same  strength.  When  the  plate  becomes  rough  or  mat  by 
the  action,  the  gas  escapes  more  freely  from  the  surface 
and  the  attack  is  more  rapid.  The  gas  evolved  contains 
no  hydrogen,  but  is  mostly  nitrous-oxide,  similarly  to  the 
action  on  zinc,  with  a  little  ammonia  gas.  The  reaction  does 
not  stop  with  the  formation  of  the  neutral  nitrate,  but  this  is 
acted  on  by  the  aluminium,  forming  a  white,  granular  precipi- 
tate of  a  basic  salt  having  the  formula :  6AI2O3.3N2O5.30H2O. 

While  cold  acid  thus  attacks  the  metal  very  slowly,  the  hot 
concentrated  acid  at  100°  attacks  it  violently. 

The  amount  of  the  action  of  cold  nitric  acid  has  been  mea- 
sured by  Le  Roy,  Lunge,  and  the  writer,  as  follows : 

*  Vide,  p.  88. 



Le  Roy,  pure,  concentrated i5"-20° 

"  commercial,  concentrated !  " 

"  "  52  per  cent !  " 

Lunge,  pure  concentrated. 
"  "     65  per  cent. . . 

"  "     32  per  cent. . . 

Richards,  pure,  concentrated. 


B      * 

6  5!" 

cJ  rt    fi 

t,  jj   -rH 

^  t/>    i^    u 







The  figure  last  given  includes  the  loss  sustained  in  polishing 
the  metal  to  its  original  appearance  before  immersion.  It  re- 
sults from  these  tests  that  a  sheet  of  aluminium  one  millimetre 
thick,  if  left  standing  in  concentrated  nitric  acid,  would  sustain 
constant  immersion  at  ordinary  temperatures  for  3600  days 
(Lunge),  43  days  (Le  Roy),  or  14  days  (Richards),  if  taken 
out  every  day  and  polished  bright. 

Concerning  the  use  of  aluminium  in  the  Grove  battery,  which 
is  not  a  constant  battery,  but  only  used  to  give  a  strong  cur- 
rent for  a  short  time,  aluminium  sheet  one  millimetre  thick 
will  last  a  long  time  and  cost  only  a  fraction  as  much  as  thin 

Hydrochloric  Acid. 

This  acid  attacks  commercial  aluminium  rapidly,  quicker 
when  hot  than  when  cold,  and  the  concentrated  quicker  than 
the  dilute.  The  very  pure  metal,  however,  is  attacked  slowly, 
showing  that,  as  with  sulphuric  acid,  the  galvanic  action  of  the 
impurities  keeping  the  aluminium  free  from  a  protecting  layer 
•of  gas,  has  a  great  influence  on  the  resistance  to  acids.  Gase- 
ous hydrochloric  acid  attacks  the  metal  even  at  a  very  low 

The   presence   of  silicon,  particularly,  increases  the  facility 


with  which  the  metal  is  attacked.  When  silicon  is  present,  the 
graphitic  silicon  remains  behind  as  a  black  residue,  while  the 
combined  silicon  partly  forms  silica  and  partly  escapes  as  sili- 
con hydride  (SiHi),  having  a  very  disagreeable  smell.  When 
the  amount  of  combined  silicon  is  small,  almost  all  of  it  may 
thus  escape.  In  analyzing  aluminium,  this  loss  is  prevented  by 
keeping  the  acid  well  oxidized  by  bromine  water,  which  pre- 
vents the  formation  of  the  gas.  On  evaporating  to  dryness,, 
after  solution,  and  taking  up  with  water,  the  graphitoidal  sili- 
con remains  as  a  black  crystalline  residue,  while  the  combined 
silicon  has  all  been  changed  to  white  silica.  These  can  be 
separated  by  washing  with  hydrofluoric  acid,  which  dissolves 
the  silica  but  leaves  the  silicon  unattacked. 

If  a  small  amount  of  hydrochloric  acid  is  present  in  a  mix- 
ture of  acids,  it  leads  the  attack  on  the  metal,  and  the  other 
acids  form  aluminium  salts  by  reacting  on  the  aluminium 
chloride  formed.  Hydrobromic,  hydriodic  and  hydrofluoric 
acids  act  similarly  to  hydrochloric.  Aluminium  fluoride,  how- 
ever, is  not  so  soluble  in  water  as  the  other  halogen  salts,  and 
the  attack  by  hydrofluoric  acid  is  therefore  hindered  by  the 
formation  of  an  insoluble  coating  on  the  aluminium  when  the 
solution  passes  a  certain  degree  of  concentration. 

In  an  experiment  by  the  writer,  best  commercial  rolled  alu- 
minium was  put  into  cold,  dilute  (3  per  cent.)  hydrochloric 
acid.  It  was  some  time  before  any  action  was  observable,  and 
then  it  was  very  slow.  It  lost,  after  cleaning,  at  the  rate  of  5S 
grammes  per  square  metre  of  surface  per  day,  which  was  only 
a  little  over  half  as  much  as  was  dissolved  by  cold,  concentrated 
nitric  acid  in  the  same  time.  A  piece  of  the  same  metal,  how- 
ever, alloyed  with  three  per  cent,  of  nickel  was  rapidly  attacked 
under  these  conditions,  and  over  thirty  times  as  much  of  it  was 
dissolved  in  a  given  time,  thus  showing  strikingly  the  influence 
of  a  small  amount  of  impurity. 

Organic  Acids,  Vinegar,  Etc. 
Deville :  "  Weak  acetic  acid  acts  on  aluminium  in  the  same 


way  as  sulphuric  acid,  i.  e.,  in  an  inappreciable  degree  or  with 
extreme  slowness.  I  used  for  the  experiment  acid  diluted  to 
the  strength  of  strongest  vinegar.  M.  Paul  Morin  left  a  plaque 
of  the  metal  a  long  time  in  wine  which  contained  tartaric  acid 
in  excess  and  acetic  acid,  and  found  the  action  on  it  quite  in- 
appreciable. The  action  of  a  mixture  of  acetic  acid  and  com 
mon  salt  in  solution  in  pure  water  on  pure  aluminium  is  quite 
different,  for  the  acetic  acid  replaces  a  portion  of  the  chlorine 
existing  in  the  sodium  chloride,  rendering  it  free.  However, 
this  action  is  very  slow,  especially  if  the  aluminium  is  pure." 

"  The  practical  results  flowing  from  these  observations  deserve 
to  be  clearly  defined,  because  of  the  applications  which  may  be 
made  of  aluminium  to  culinary  vessels.  I  have  observed  that 
the  tin  so  often  used  and  which  each  day  is  put  in  contact  with 
common  salt  and  vinegar,  is  attacked  much  more  rapidly  than 
aluminium  under  the  same  circumstances.  Although  the  salts 
of  tin  are  very  poisonous,  and  their  action  on  the  economy  far 
from  being  negligible,  the  presence  of  tin  in  our  food  passes  un- 
perceived  because  of  its  minute  quantity.  Under  the  same 
circumstances  aluminium  dissolves  in  less  quantity;  the  acetate 
of  aluminium  formed  resolves  itself  on  boiling  into  insoluble 
alumina  or  an  insoluble  sub-acetate,  having  no  more  taste  or 
action  on  the  body  than  clay  itself.  It  is  for  that  reason  and 
because  it  is  known  that  the  salts  of  the  metal  have  no  appre- 
ciable action  on  the  body,  that  aluminium  may  be  considered 
as  an  absolutely  harmless  metal." 

The  low  price  of  aluminium  has  within  the  last  two  years 
rendered  possible  this  application  to  culinary  utensils  foreseen 
by  Deville,  and  has  led  to  several  investigations  as  to  its  resist- 
ance to  the  acids  and  salts  liable  to  be  met  with  in  food. 

Two  German  pharmacists,  Lubbert  and  Roscher,  conducted 
tests  of  this  kind  in  1891,  but  their  results  were  only  qualitative, 
not  quantitative,  and  they  made  the  mistake  of  using  thin 
aluminium  foil,  which  averages  only  o.ooi  inch  thick,  instead 
of  heavier  sheet.  The  result  was  that  they  found  their  thin  foil 
totally  dissolved  by  two   days   immersion  in  oxalic  acid  (1,5 


and  lO  per  cent.),  gallic  acid  (2  per  cent.),  and  corrosive  sub- 
limate (i  per  cent.)  ;  and  by  four  days  constant  immersion  in 
I,  5  and  10  per  cent,  solutions  of  formic,  acetic,  butyric,  lactic,, 
tartaric  and  citric  acids,  pure  oleic  acid,  10  per  cent,  solutions 
of  palmitic  or  stearic  acids,  in  5  per  cent,  solutions  of  carbolic 
acid,  4  per  cent,  solution  of  boric  acid,  and  in  pure  red  wine, 
white  wine,  coffee  and  tea. 

It  has  been  found,  however,  that  because  of  its  thinness  alu- 
minium foil  does  not  resist  corrosion  as  does  the  heavier  sheet- 
metal,  and  while  the  above  results  may  be  strictly  true  for  foil 
0.00 1  inch  thick,  yet  ordinary  sheet  aluminium  is  not  attacked 
to  anything  like  such  an  extent.  Culinary  utensils  are  made  of 
sheet  at  least  i  millimetre  (0.04  inch)  thick,  and  tests  of  mate- 
rial of  this  thickness  made  by  subsequent  investigators  have 
given  very  different  results. 

Balland*  conducted  tests  for  several  months,  and  found  that 
air,  water,  wine,  beer,  cider,  coffee,  milk,  oil,  butter,  fat,  urine, 
saliva  and  damp  earth  have  less  action  on  aluminium  than  on 
iron,  copper,  lead,  zinc,  or  tin.  Vinegar  and  salt  together  at- 
tack it,  but  so  slightly  as  not  to  prevent  its  use  for  cooking;  a 
sheet  only  lost  1.3  per  cent,  of  its  weight  in  vinegar,  and  0.2 
per  cent,  of  its  weight  in  a  5  per  cent,  salt  solution  after  four 
months'  immersion. 

Ruppf  states  that  he  has  kept  different  kinds  of  liquid  and 
semi-solid  food  in  aluminium  vessels  for  4  to  28  days,  at  the 
ordinary  temperature,  and  found  the  metal  unaltered.  The 
metal  used  contained  0.30  per  cent,  of  iron,  0.08  silicon  and 
99.66  aluminum. 

Prof.  Geo.  Lunge, |  of  Zurich,  has  made  a  most  careful  and 
systematic  investigation  of  this  subject.  Assisted  by  Ernst 
Schmid,  he  made  the  following  series  of  tests ;  ordinary  com- 
mercial sheet  aluminum  from  Neuhausen  was  used.  It  ana- 
lyzed : 

*  Comptes  Rendus,  1892,  Vol.  114,  p.  1536. 

t  Chronique  Industrielle,  June  12,  1892. 

I  Zeitschrift  fiir  angewandte  Chemie,  January,  1892. 


Aluminium 99.20  per  cent,  (by  difference) 

Combined  silicon 0.44       " 

Graphitic       "      o.i  I       " 

Iron   0.25        " 

Copper trace. 

The  sheet  was  i  minimetre  thick,  and  was  cut  into  strips  of 
a  fixed  size.  These  were  first  carefully  cleaned  by  caustic  soda 
and  sulphuric  acid,  and  then  immersed  six  days  in  the  liquids 
at  the  ordinary  temperature,  each  liquid  being  tested  twice  to 
guard  againt  mistakes.  The  following  are  their  results,  ex- 
pressed as  the  weight  dissolved  per  day  in  milligrammes  per 
square  metre  of  surface  exposed  : 

Loss  of  weight  per  day  in 
milligrammes  per  square 

Liquid.                                                                     i  metre  of  surface. 

Ordinary  claret 47.3 

"         hock 51.2 

Brandy 18.0 

Pure  50  per  cent,  alcohol 10.2 

Tartaric  acid,  5  per  cent,  solution 28.2 

"           '■     I       "                " 43.0 

Acetic        "     S       "               "       .64.2 

"            "     I       "               "       73.0 

Citric          "     5       "                "        35-8 

"     I       "               "       31-7 

Lactic        "     5       "               "       ■■■■■  79-5 

Butyric       "     5       "                "       21.8 

Carbolic     "     5       "               "       3-8 

"           "     1       "              ••       8.2 

Boric           "     4       "                "        29.5 

Salicylic     "    I4      "                "        105.8 

Coffee  (poured  hot) 8.3 

Tea                  "        00 

Beer o-o 

The  aluminium  strips  used  showed  outward  evidences  of 
corrosion  in  only  a  few  places ;  only  in  the  case  of  the  salicylic 
acid  solution  had  the  metal  lost  its  bright  surface  and  become 
dull.  In  the  case  of  brandy  and  alcohol,  where  the  quantitative 
action  was  very  slight,  the  surface  of  the  aluminium  showed  a 
few  fungus-like  excresences,  probably  formed  by  alumina, 
caused  by  accidental  flaws  in  the  sheet.     In  the  case  of  a  wine 


rich  in  tannin,  these  spots  are  liable  to  be  darkened  by  the  in- 
fluence of  the  trace  of  iron  dissolved  from  the  aluminium,  form- 
ing tannate  of  iron,  but  the  amount  thus  formed  is  infinitesmal. 
The  weights  dissolved  are  so  extremely  small,  that  it  may  be 
calculated  that  a  canteen  holding  a  litre  could  be  kept  full  of 
the  strong  acetic  acid  for  55  years  before  losing  half  its  weight. 

Lunge  and  Schmid  conclude  that,  "  the  action  of  coffee,  tea 
and  beer  is  practically  zero ;  that  of  acids  and  acid  liquids  is 
more  pronounced,  but  in  the  worst  case  too  slight  to  cause  any 
alarm  whatever.  Nor  is  there  the  slightest  danger  of  any  in- 
jurious action  on  the  human  body  by  such  traces  of  aluminium 
compounds,  seeing  that  our  food  contains  very  much  more  than 
these ;  in  fact,  they  could  not  act  injuriously  unless  quantities 
hundreds  of  times  larger  were  regularly  entering  the  stomach." 

The  only  criticism  we  have  to  make  of  this  valuable  investiga- 
tion is  that  the  solutions  should  have  been  tested  hot,  even 
boiling,  as  well  as  cold.  While  it  is  perfectly  true,  as  remarked 
by  a  Washington  lady,  that  "  we  hope  never  to  have  occasion 
to  serve  our  families  with  poisoned  soups  or  salicylic  or  boracic 
acid  stews,"  yet  if  Lunge  had  made  the  hot-liquid  tests  we 
should,  at  least,  have  known  the  worst  that  could  possibly  hap- 
pen to  the  aluminium  culinary  utensils. 

Happily,  actual  experience  has  settled  all  these  questions. 
An  aluminium  sauce-pan  used  in  the  writer's  family  constantly 
for  two  years,  which  has  been  used  for  boiling  milk,  cooking 
oatmeal  and  vegetables,  stewing  meats  and  preserving  several 
kinds  of  fruits,  lost  less  than  one-quarter  ounce  in  the  whole  two 
years,  an  average  of  less  than  15  milligrammes  per  day  per 
square  metre  of  surface  exposed,  including  frequent  cleaning. 
I  have  calculated  that  at  this  rate  the  utensil  will  become  a  fam- 
ily heirloom  unless  accident  overtakes  it,  for  it  could  stand  this 
rate  of  wear  for  over  a  century  before  losing  half  its  weight. 
Other  experiences  equally  as  striking  could  be  cited,  and  no 
better  proof  of  the  suitability  of  aluminium  for  culinary  utensils 
could  be  wished.  The  German  Minister  of  War,  after  thorough 
experiments  by  an  army  commission,  has  adopted   aluminium 


canteens  and  drinking  cups  for  the  soldiers,  and  entire  sets  of 
cooking  utensils  for  use  in  the  officers'  quarters.  It  is  the 
writer's  opinion  that  within  a  short  time  the  larger  part  of  all 
the  aluminium  made  will  be  needed  to  supply  the  great  demand 
which  will  arise  for  these  culinary  utensils. 

Sodium  Chloride. 

Common  salt  does  not,  when  molten,  corrode  aluminium,  so 
that  it  forms  a  good  flux  to  melt  the  metal  with.  It  does  not 
possess  the  property,  like  fluorspar,  of  dissolving  alumina,  but 
acts  simply  by  its  fluidity  to  give  a  clean  melt. 

A  solution  of  common  salt  acts  very  feebly  on  aluminium. 
A  strip  of  rolled  aluminium  immersed  in  a  three  per  cent,  solu- 
tion at  27°  C.  lost  weight  at  the  rate  of  394  milligrammes  per 
day  per  square  metre  of  surface  (Hunt).  The  writer  found  a 
corresponding  loss  of  400  milligrammes  per  day  on  sheet  im- 
mersed in  a  strong  brine  kept  at  65°  C.  (150°  F.)  At  that 
rate  it  would  take  nine  years'  constant  immersion  to  entirely 
dissolve  a  sheet  one  millimetre  thick. 

When  an  acid  is  present  with  the  salt,  the  action  is  stronger 
than  when  either  is  alone.  Mr.  Hunt  found  that  when  two 
per  cent,  of  acetic  acid  was  added  to  the  salt  solution  previously 
mentioned,  the  corrosion  was  increased  to  1738  milligrammes 
per  day.  This  solution  will  fairly  represent  the  extreme  con- 
ditions to  which  aluminium  will  be  subjected  in  domestic  culi- 
nary operations,  and  shows  that  the  corrosion  is  so  slight  as  to 
be  of  no  practical  consequence,  being  much  less  than  copper, 
tin-plate  or  iron  would  sufifer  under  similar  conditions. 

Sea-water  corrodes  aluminium  slightly,  but  much  less  than 
iron  or  steel,  under  similar  conditions.  Strips  of  aluminium 
on  the  sides  of  a  wooden  sailing  vessel  lost  less  than  100  milli- 
grammes per  square  metre  of  surface  during  six  months'  ex- 
posure (Hunt).  Messrs.  Yarrow  &  Co.,  on  the  Thames, 
having  in  view  the  building  of  an  aluminium  torpedo  boat  for 
the  French  government,  took  two  plates  of  aluminium  stiffened 
by  alloying  with  six  per  cent,  of  copper,  and  after  weighing 


accurately  secured  them  on  the  sides  of  a  wooden,  coppered 
sailing  vessel,  the  copper  being  removed  to  make  place  for 
the  aluminium.  This  ship  made  a  voyage  round  the  world ; 
then  the  aluminium  plates  were  removed,  weighed,  and  found 
to  have  suffered  no  appreciable  loss.  As  a  consequence  of  this 
result,  Messrs.  Yarrow  proceeded  with  the  construction  of  the 
boat,  which  is  the  largest  vessel  yet  built  of  aluminium,  having 
a  length  of  sixty  feet,  beam  nine  feet  three  inches  and  a  maxi- 
mum speed  of  twenty-two  knots  (twenty-five  and  one-half 
miles)  per  hour. 

It  is  to  be  recommended,  however,  that  aluminium  hulls  in- 
tended for  salt  water  should  be  painted,  in  order  to  reduce  any 
possible  corrosion  to  a  minimum. 

Organic  Secretions. 

These  act  only  slightly  on  aluminium,  the  degree  of  corrosion 
being  proportioned  mostly  to  the  amount  of  sodium  chloride 
present  in  the  secretion  and  its  degree  of  acidity,  or,  particu- 
larly, of  alkalinity.  The  saliva  acts  on  it  so  slightly  that  alu- 
minium dental  plates  may  be  worn  for  many  years  without  any 
appreciable  corrosion.  M.  Charriere,  a  French  physician,  was 
the  first  to  make  a  small  tube  of  it  for  a  person  on  whom  trache- 
otomy had  been  performed.  He  found  it  to  remain  almost 
unaltered  by  contact  with  purulent  matter ;  after  a  long  time  a 
little  alumina  was  formed  on  it,  hardly  enough  to  be  visible. 
The  use  of  aluminium  for  suture  wire  is  also  highly  recom- 
mended ;  many  instruments  for  physician's  use  are  being  made 
of  aluminium,  its  great  advantages  being  lightness,  incorrodibil- 
ity,  and  being  so  easily  cleansed,  particularly  by  antiseptic 
solutions.  The  tarnishing  of  polished  aluminium  articles  when 
constantly  handled  is  due  to  the  perspiration,  which  contains 
about  two  per  cent,  of  sodium  chloride  and  about  an  equal 
quantity  of  organic  acids.  Its  action  is  not  very  strong,  yet 
sufficient  to  spoil  a  high  polish  and  give  a  visible  tarnish,  as 
would  indeed  happen  to  almost  any  other  metal.  If,  however, 
the  perspiration  is  profuse  and  acts  on  the  aluminium  con- 


stantly  while  warm,  a  deeper  corrosion  results.  I  have  seen  an 
aluminium  ankle-stiffener,  of  metal  about  one  millimetre  thick, 
which  was  worn  in  the  heel  of  a  boot  for  about  a  year,  and  was 
then  eaten  nearly  through  by  the  corrosion  due  to  perspiration 
a  little  above  the  ankle.  The  shoe  lining  which  covered  it  had 
served  to  keep  it  constantly  in  contact  with  the  perspiration, 
while  the  temperature  may  have  been  about  85°  C.  This  is, 
however,  an  extreme  case,  and  it  would  be  interesting  to  know 
whether  steel  or  very  stifif  leather  would  have  lasted  as  long_ 
under  the  same  circumstances. 

Caustic  Alkalies. 

Deville :  "  Solutions  of  caustic  potash  or  caustic  soda  ict' 
with  great  energy  on  aluminium,  transforming  it  into  aluminate 
of  potash  or  soda,  setting  free  hydrogen.  However,  it  is  not 
attacked  by  caustic  potash  or  soda  in  fusion ;  one  may,  in  fact, 
drop  a  globule  of  the  pure  metal  into  melted  caustic  soda  raised 
almost  to  red  heat  in  a  silver  vessel,  without  observing  the 
least  disengagement  of  hydrogen.  Silicon,  on  the  contrary, 
dissolves  with  great  energy  under  the  same  circumstances.  I 
have  employed  melted  caustic  soda  to  clean  siliceous  alumin- 
ium. The  piece  is  dipped  into  the  bath  kept  almost  at  red 
heat.  At  the  moment  of  immersion  several  bubbles  of  hydro- 
gen disengage  from  the  metallic  surface,  and  when  they  have 
disappeared  all  the  silicon  of  the  superficial  layer  of  aluminium 
has  been  dissolved.  It  only  remains  to  wash  well  with  water 
and  dip  it  into  nitric  acid,  when  the  aluminium  takes  a  beautiful 

Mallet  found  that  the  purest  aluminium  resists  the  caustic 
alkaline  solution  better  than  the  commercial  metal.  I  have- 
noticed  the  same  fact  in  comparing  aluminium  of  different 
degrees  of  purity;  best  commercial  metal  withstood  the  action 
of  cold,  dilute  caustic  potash  solution  seven  times  better  than 
when  it  contained  three  per  cent,  of  copper,  and  seventy  times 
better  than  when  two  per  cent,  of  copper  and  one  per  cent,  of 
zinc  were  present. 


Prof.  A.  Stutzer,*  of  Bonn,  finds  that  the  metal  made  by  the 
electrolytic  processes  dissolves  much  slower  than  that  made  by 
the  former  sodium  processes.  He  ascribes  this  to  the  latter 
metal  containing  nearly  one  per  cent,  of  sodium.  This,  how- 
ever, can  hardly  be  the  case,  because  metal  made  by  the  Deville 
process  rarely  contained  more  than  a  trace  of  sodium.  The  true 
reason  must  be  simply  the  greater  purity  of  the  metal  now  be- 
ing made  by  electrolysis,  which  averages  over  99  per  cent,  pure 
for  best  quality  metal,  while  the  Deville  metal  was  rarely  over 
98  per  cent.  pure. 


Aqua  ammonia  acts  slowly  on  aluminium,  producing  a  little 
alumina,  part  of  which  remains  dissolved.     Ammonia  gas  does  • 
not  appear  to  act  on  the  metal. 

Lime  Water. 

This  acts  rapidly  on  aluminium  at  first,  but  the  resulting 
calcium  aluminate  is  insoluble  in  water,  and  is,  therefore,  pre- 
cipitated on  the  metal  and  quickly  protects  it  from  further 
action.     If  this  coating  is  scraped  off  the  action  is  repeated. 

Solutions  of  Metallic  Salts. 
Deville  :  "  The  action  of  any  salt  whatever  on  aluminium  may 
be  easily  deduced  from  the  action  of  its  acids  on  that  metal.  ' 
We  may,  therefore,  predict  that  in  acid  solutions  of  sulphates 
and  nitrates  aluminium  will  precipitate  no  metal,  not  even 
silver,  as  Wohler  has  observed.  But  the  hydrochloric  solutions 
of  the  same  metal  will  be  precipitated,  as  MM.  Tissier  have 
shown.  Likewise,  in  alkaline  solutions,  silver,  lead,  and  metals 
high  in  the  classification  of  the  elements  are  precipitated.  It 
may  be  concluded  from  this  that  to  deposit  aluminium  on  other 
metals  by  means  of  the  battery,  it  is  always  necessary  to  use 
acid  solutions  from  which  hydrochloric  acid,  free  or  combined, 
.should  be  absent.     For  similar  reasons  the  alkaline  solutions  of 

*  Zeitschr.  fiir  angewandte  Chemie,  1890,  No.  23. 


the  same  metals  cannot  be  employed,  although  they  give  such 
good  results  in  plating  common  metals  with  gold  and  silver.  It 
is  because  of  these  curious  properties  that  gilding  and  silvering 
aluminium  are  so  difficult." 

These  conclusions  by  Deville  are  confirmed  only  when  using 
pure  aluminium;  the  impure  metal,  containing  iron,  silicon,  or 
perhaps  sodium,  may  produce  very  slight  precipitates  in  cases 
where  pure  aluminium  would  produce  none.  Some  observers 
have  noted  different  results  in  some  cases  even  when  using  alu- 
minium free  from  these  impurities.  We  will  therefore  take  up 
these  cases  and  consider  them  separately. 

Mercury. — *  Aluminium  decomposes  solutions  of  mercuric 
chloride,  cyanide  or  nitrate,  mercury  separating  out  first,  then 
forming  an  amalgam  with  the  aluminium  which  is  immediately 
decomposed  by  the  water,  the  result  being  alumina  and  mer- 
cury. From  an  alcoholic  solution  of  mercurous  chloride  the 
mercury  is  precipitated  more  quickly  at  a  gentle  heat.  A  solu- 
tion of  mercurous  iodide  with  potassium  iodide  is  also  reduced 
in  like  manner. 

Copper. — *  From  solution  of  copper  sulphate  or  nitrate,  alu- 
minium separates  out  copper  only  after  two  days'  standing,  as 
either  dendrites  or  octahedra ;  from  the  nitrate  it  also  precipi- 
tates a  green,  insoluble  basic  salt.  Copper  is  precipitated 
immediately  from  a  solution  of  cupric  chloride;  but  slower 
from  the  solution  of  copper  acetate.  The  sulphate  or  nitrate 
solutions  behave  similarly  if  potassium  chloride  is  also  present, 
and  the  precipitation  is  complete  in  presence  of  excess  of  alu- 

Silver. — *From  a  nitrate  solution,  feebly  acid  or  neutral, 
aluminium  precipitates  silver  in  dendrites,  the  separation  only 
beginning  after  six  hours'  standing.  From  an  ammoniacal 
solution  of  silver  chloride  or  chromate,  aluminium  precipitates 
the  silver  immediately  as  a  crystalline  powder.  Cossa  con- 
firms the  statement  as  to  the  nitrate  solution. 

Lead. — *  From  nitrate  or  acetate  solution  the  lead  is  slowly 

*  Dr.  Mierzinski. 


precipitated  in  crystals ;  an  alkaline  solution  of  lead  chromate 
gives  precipitates  of  lead  and  chromic  oxide. 

Zinc. — *  An  alkaline  solution  of  zinc  salt  is  readily  decom- 
posed and  zinc  precipitated. 

Margottet  states  that  all  metallic  chlorides  excepting  those 
of  potassium  or  sodium  are  reduced  from  solution.  This  state- 
ment can  hardly  include  chlorides  of  magnesium  or  lithium, 
since  magnesium  precipitates  alumina  from  solutions  of  alu- 
minium salts.  Alkaline  or  ammoniacal  solutions  are  more 
easily  decomposed  than  acid  solutions ;  in  alkaline  solutions 
the  cause  being  the  facility  with  which  aluminates  of  the  alka- 
lies are  formed. 

Alkaline  Chlorides. — A  solution  of  sodium  or  potassium 
chlorides  is  not  appreciably  affected  by  pure  aluminium,  either 
cold  or  warm.  However,  rather  impure  aluminium  which  was 
packed  in  a  case  with  saw-dust  and  kept  wet  with  sea-water  for 
two  weeks  was  corroded ;  whether  the  result  would  have  been 
the  same  without  the  presence  of  the  saw-dust  or  with  purer 
aluminium,  I  cannot  say. 

Aluminium  Salts. — It  is  a  curious  fact  that  a  solution  of  alu- 
minium chloride  will  attack  aluminium,  forming  a  basic-chloride 
with  evolution  of  hydrogen.  A  solution  of  alum  does  not  attack 
aluminium,  but  if  sodium  chloride  is  added  it  is  dissolved  with 
evolution  of  hydrogen.  It  is  interesting  to  note  that  while 
neither  of  these  salts  alone  attacks  aluminium,  the  mixture  of 
the  two  does. 

Fluorspar  on  being  melted  gives  off  a  little  hydroflouric  acid 
vapor,  caused  by  the  action  of  the  hydroscopic  moisture  in  it. 
This  vapor  will  attack  aluminium,  forming  fluoride.  Aside 
from  this  slight  action,  the  molten  fluorspar  has  no  action  on 
the  aluminium.  It  has,  however,  the  property  of  dissolving 
a  small  proportion  (about  2  per  cent.)  of  alumina,  and  this 
action    causes    it   to    be  a  very   efficient  flux,  because    small 

*  A.  Cossa,  Bull,  de  la  Soc.  Chim.,  1870,  p.  199. 


globules  of  aluminium  are  usually  encrusted  with  a  thin  film 
of  alumina  which  prevents  them  from  running  together  to  a  but- 
ton. The  fluorspar,  by  dissolving  this  coating  and  affording  a 
fluid  mass,  fluxes  the  separated  globules  together.  It  is  often 
used  in  connection  with  cryolite  and  common  salt. 


Melted  cryolite  is  a  very  good  flux  for  aluminium,  for  the 
same  reason  as  described  under  fluorspar.  It  can,  however, 
dissolve  over  20  per  cent,  of  alumina,  and  is  therefore  that 
much  more  efficient  as  a  fluxing  agent.  At  a  temperature 
above  the  melting  point  of  copper  it  attacks  the  aluminium 
itself,  if  it  is  put  into  it  finely  divided,  but  the  metal  en  masse 
is  not  sensibly  attacked.  The  result  of  this  attack  must  be  the 
formation  of  a  sub-fluoride,  possibly  AIF2. 

Silicates  and  Borates. 

Neither  of  these  classes  of  compounds  can  be  used  as  fluxes 
or  slags  in  working  aluminium,  since  they  both  rapidly  corrode 
the  metal.  Deville  had  little  difficulty  in  decomposing  these 
salts  so  completely  with  metallic  aluminium  that  he  isolated 
silicon  and  boron.  If  aluminium  is  melted  in  an  ordinary 
glass  vessel  it  attacks  it,  setting  free  silicon  from  silica,  forming 
an  aluminate  with  the  alkali  present  and  an  alloy  with  the  sili- 
con set  free.  Aluminium  melted  under  borax  is  rapidly  dis- 
solved, an  aluminium  borate  being  formed.  It  is  thus  seen 
that  the  common  metallurgic  slags  are  altogether  excluded 
from  the  manufacture  of  aluminium,  and  also  that  it  is  an  im- 
possibility to  manufacture  pure  aluminium  direct  from  minerals 
containing  silica.  The  result  of  reducing  kaolin,  for  instance, 
would  inevitably  be  highly  siliceous  aluminium,  from  which 
there  is  no  known  method  of  separating  out  pure  aluminium. 
These  facts  also  point  to  the  importance  of  keeping  molten 
aluminium  from  contact  with  the  ordinary  siliceous  refractory 
materials  in  working  it.  Even  the  best  quality  plumbago 
crucibles  will  increase  the  percentage  of  silicon  in  commercial 


aluminium  at  least  0.25  per  cent,  at  one  melting.  Magnesia 
brick  linings  and  magnesia-lined  crucibles  should  be  used  for 
melting  it  in. 


Deville  :  "  Aluminium  may  be  melted  in  nitre  without  under- 
going the  least  alteration,  the  two  materials  rest  in  contact 
without  reacting  even  at  a  red  heat,  at  which  temperature  the 
salt  is  plainly  decomposed,  disengaging  oxygen  actively.  But 
if  the  heat  is  pushed  to  the  point  where  nitrogen  itself  is  disen- 
gaged, there  the  nitre  becomes  potassa,  a  new  affinity  becomes 
manifest,  and  the  phenomena  change.  The  metal  then  com- 
bines rapidly  with  the  potassa  to  give  aluminate  of  potash. 
The  accompanying  phenomenon  of  flagration  often  indicates  a 
very  energetic  reaction.  Aluminium  is  continually  melted  with 
nitre  at  a  red  heat  to  purify  it  by  the  oxygen  disengaged,  with- 
out any  fear  of  loss.  But  it  is  necessary  to  be  very  careful  in 
doing  it  in  an  earthen  crucible.  The  silica  of  the  crucible  is 
dissolved  by  the  nitre,  the  glass  thus  formed  is  decomposed  by 
the  aluminium,  and  the  silicide  of  aluminium  formed  is  then 
very  oxidizable,  especially  in  the  presence  of  alkalies.  The 
purification  by  nitre  ought  to  be  made  in  an  iron  crucible  well 
oxidized  by  nitre  inside." 

If  finely  divided  aluminium  is  mixed  with  nitre  and  brought 
to  a  red  heat,  the  metal  is  oxidized  with  the  production  of  a 
fine  blue  flame.  (Mierzinski.)  Nitre  is  also  used  sometimes 
in  the  composition  of  aluminium  flash-light  powders. 

Alkaline  Sulphates  and  Carbonates. 
Tissier :  "Only  2.65  grammes  of  aluminium  introduced  into 
melted  red-hot  sodium  sulphate  (NajSOj)  decomposed  that 
salt  with  such  intensity  that  the  crucible  was  broken  into  a 
thousand  pieces,  and  the  door  of  the  furnace  blown  to  a  dis- 
tance. Heated  to  redness  with  alkaline  carbonate,  the  alu- 
minium was  slowly  oxidized  at  the  expense  of  the  carbonic 
acid,  carbon  was  set  free,  and  an  aluminate  formed.  The  re- 
action takes  place  without  deflagration." 

chemical  properties  of  aluminium.  i05 

Metallic  Oxides. 

Tissier  Brothers  made  a  series  of  experiments  on  the  action 
of  aluminium  on  metallic  oxides.  Aluminium  leaf  was  care- 
fully mixed  with  the  oxide,  the  mixture  placed  in  a  small  por- 
celain capsule  and  heated  in  a  small  earthen  crucible,  which 
served  as  a  muffle.     The  results  were  as  follows : 

Manganese  dioxide. — No  reaction. 

Zinc  oxide. — No  reaction  even  at  white  heat. 

Ferric  oxide. — By  heating  to  white  heat  one  equivalent  of 
ferric  oxide  and  three  of  aluminium,  the  reaction  took  place 
with  detonation,  and  by  heating  sufficiently  we  obtained  a 
metallic  button,  well  melted,  containing  69.3  per  cent,  of  iron 
and  30.7  per  cent,  of  aluminium.  Its  composition  corresponds 
very  nearly  to  the  formula  AlFe.  It  would  thus  appear  that 
the  decomposition  of  ferric  oxide  will  not  pass  the  limit  where 
the  quantity  of  iron  reduced  is  sufficient  to  form  with  the  alu- 
minium the  alloy  AlFe. 

Lead  oxide. — We  mixed  two  equivalents  of  litharge  with  one 
of  aluminium,  and  heated  the  mixture  slowly  up  to  white  heat, 
when  the  latter  reacted  on  the  litharge  with  such  intensity  as 
to  produce  a  strong  detonation.  We  made  an  experiment  with 
fifty  grammes  of  litharge  and  2.9  grammes  of  aluminium  leaf, 
when  the  crucible  was  broken  to  pieces  and  the  doors  of  the 
furnace  blown  off. 

Copper  oxide. — Three  grammes  of  black  oxide  of  copper 
mixed  with  1.03  grammes  of  aluminium  detonated,  producing 
a  strong  explosion,  when  the  heat  reached  whiteness. 

Beketoff"*  reduced  baryta  (BaO)  with  metallic  aluminium  in 
excess,  and  obtained  alloys  of  aluminium  and  barium  contain- 
ing in  one  case  twenty-four  per  cent.,  in  another  thirty-three 
per  cent,  of  barium. 

If  any  of  the  metallic  oxides  are  fluxed,  as  by  being  dis- 
solved in  cryolite,  metallic  aluminium  reduces  them  to  metal  at 
once.     Messrs.  Green  and  Wahl  have  patented  this  method  of 

*  Bull,  de  la  Soc.  Chimique,  1887,  p.  22. 


producing  pure  metallic  manganese,  which  is  at  present  being 
put  into  operation  in  Philadelphia  on  a  commercial  scale. 

Miscellaneous  Agents. 

Phosphate  of  lime. — Tissier  Brothers  heated  to  whiteness  a 
mixture  of  calcium  phosphate  with  aluminium  leaf,  without  the 
metal  losing  its  metallic  appearance  or  any  reaction  being 

Hydrogen. — This  gas  appears  to  have  no  action  on  alumin- 
ium, except  to  be  dissolved  in  it  in  a  moderately  large  quantity. 

Chlorine. — Gaseous  chlorine  attacks  the  metal  rapidly.  Alu- 
minium foil  heated  in  an  atmosphere  of  chlorine  takes  fire  and 
burns  with  a  vivid  light. 

Bromine,  iodine,  act  similarly  to  chlorine. 

Fluorine. — Fluorine  gas  forms  a  thin  coating  of  fluoride  which 
prevents  a  deeper  attack.  If  the  metal  is  at  a  dark-red  heat,  a 
violent  incandescence  ensues,  and  the  attack  is  very  energetic. 
Under  the  microscope  the  residue  is  seen  to  be  globules  of  alu- 
minium covered  with  uncrystallized  fluoride. 

Silver  chloride. — Fused  silver  chloride  is  decomposed  by 
aluminium,  the  liberated  silver  as  well  as  the  excess  of  alumin- 
ium being  melted  by  the  heat  of  the  reaction. 

Mercurous  chloride. — If  vapors  of  mercurous  chloride  are 
passed  through  a  tube  in  which  some  hot  aluminium  is  placed, 
mercury  is  separated  out,  aluminium  chloride  deposits  in  the 
cooler  part  of  the  tube,  and  the  aluminium  is  melted  by  the 
heat  developed. 

Carbonic  oxide. — Aluminium  acts  on  this  gas,  forming  alu- 
mina and  setting  free  carbon.  Prof.  Arnold  proved  this  by 
taking  molten  steel  of  a  known  content  of  carbon,  and  after 
adding  to  it  several  per  cent,  of  aluminium,  he  passed  a  current 
of  this  gas  through  it  for  one  hour.  A  sample  of  the  metal 
subsequently  analyzed  showed  one-third  more  carbon  than 
before  the  treatment.  This  reaction  is  one  of  the  causes  of 
the  advantage  of  adding  aluminium  to  molten  steel,  as  it  thus 
jemoves  one  of  the  gases  which  form  blow-holes  in  the  cast- 



In  this  chapter  we  propose  to  note  in  rather  condensed  form 
the  prominent  characteristics  of  the  various  aluminium  com- 
pounds, with  an  outline  of  the  methods  by  which  they  can  be 
produced,  reserving  for  another  chapter,  however,  the  prepara- 
tion of  those  salts  which  are  now  being  manufactured  on  a 
commercial  scale  for  purposes  of  further  treatment  for  alumin- 
ium. I  do  not  propose  this  as  a  substitute  for  the  various 
chemical  treatises  on  this  subject,  but  simply  to  add  to  the 
completeness  of  this  work  in  order  that  a  fair  understanding  of 
the  other  parts  of  the  book  may  not  be  missed  because  data  of 
this  nature  are  not  immediately  at  hand.  Parts  of  this  chapter 
are  taken  from  M.  Margottet's  treatise  on  aluminium,  in 
Fremy's  Enclycopedie  Chimique. 

General  Considerations. 

Position  of  aluminium  in  the  periodic  classification  of  the  ele- 
ments.— Mendeleeff  places  aluminium  in  his  third  family  of 
elements,  it  being  preceded  by  boron,  and  followed  by  the  rare 
elements  scandium,  gallium,  yttrium,  indium,  didymium,  erbium 
and  thallium.  These  elements  all  form  oxides  of  the  same 
general  form,  R2O3,  and  their  other  chemical  compounds  are 
■correspondingly  similar.  As  we  have  zinc,  cadmium  and  mer- 
cury as  the  analogues  of  magnesium  in  the  second  group,  so  we 
have  gallium,  indium  and  thallium  as  the  corresponding  ana- 
logues of  aluminium  in  the  third  group.  Unfortunately,  these 
elements  are  so  rare  that  we  are  not  so  familiar  with  their  prop- 
erties as  we  could  wish.  We  can  notice,  however,  that  as  the 
atomic  weight  increases  the  specific  gravity  and  the  atomic 

(107  ) 


volume  increase  also,  while  the  compounds  formed  by  these 
metals  become  more  easily  decomposable.     For  instance : 

Element.  Atomic  Weight.  Specific  Gravity.  Atomic  Volume. 

Boron ii  2.5  4.5 

Aluminium 27  2.7  10 

Gallium 70  5.9  12 

Indium  113  7.4  14 

Thallium 204  11.8  17 

Structure  of  aluminium  compounds. — Aluminium  has  until  re- 
cently been  regarded  as  a  quadrivalent  element,  for  the  reason 
that  no  compound  was  known  whose  molecule  contained  less  than 
two  atoms  of  aluminium  combined  with  six  atoms  of  a  mono- 
valent element.  Thus,  the  oxide  was  AI2O3,  the  chloride  AhCle,, 
etc.  It  was,  therefore,  supposed  that  in  the  molecule  of  every 
aluminium  compound  the  two  atoms  of  aluminium  were  held 
together  by  an  exchange  of  one  bond,  and  since  each  atom  had 
three  bonds  left  over,  it  was  supposed  that  each  single  alumin- 
ium atom  had  four  bonds  or  affinities.  The  composition  of  the 
oxide  and  chloride  were  therefore  represented  graphically  as. 
follows : 

r  O  -,  Cl     cl 

0  =  A1— A1  =  0  Cl  — Al  — Al  — Cl 

A       dl 

The  two  atoms  of  aluminium,  having  six  free  affinities,  were 
spoken  of  as  a  "  double  hexad-atom." 

All  this  reasoning,  however,  has  broken  down  since  the  dis- 
covery of  compounds  containing  only  one  atom  of  aluminium! 
in  a  molecule,  and  in  which  the  aluminium  is  undoudtedly  tri- 
valent;  such  are  the  organic  salts  A^CHa),,  A1(C2H5)3,. 
A1(C5H702)3.  In  the  latter  salt,  the  vapor  density  corresponds 
to  the  formula  given  at  only  45°  above  its  melting  point- 
Even  aluminium  chloride  itself  has  been  proven  to  have  the 
formula  AlCls  when  its  vapor  density  is  taken  at  a  temperature 
above  800°.     We  are  therefore  constrained  to  drop  the  former 


ideas,    and    consider    aluminium    as   tri-valent.     The   graphic 
formulae  given  above  must  then  be  written 

0  =  A1  — O  — Al  =  o  Cl  — Al  — Cl 

The  tri-valency  of  aluminium  is  also  required  by  its  position 
in  the  list  of  elements.  Thus  we  have,  taking  the  elements 
immediately  preceding  and  following  it : 

Atomic  Weight.  Valence  in  organic  salts 

Sodium 23  I 

Magnesium 24  2 

Aluminium 27  3 

Silicon 28  4 

Phosphorus 31  3 

Sulphur 32  2 

Chlorine 353^  i 

Aluminium  acts  as  a  feeble  base  or  a  rather  strong  acid.  As 
a  base  it  has  many  analogies  with  iron  in  ferric  compounds. 
For  instance,  the  oxides  AlzOs  and  FcjOg  crystallize  in  the  same 
iorms,  rhombohedra,  with  almost  exactly  the  same  fundamen- 
tal angles,  while  the  native  hydrous  oxides  AI2O3.H2O  and 
Fe^Os.HjO,  both  crystallize  in  the  orthorhombic  system  with 
very  similar  angles  and  cleavages.  As  an  acid,  it  forms  com- 
pounds analogous  to  ferric  and  chromic  acids.     For  instance : 

Aluminate  of  iron ^. FeAl^O,. 

Ferrate       "     "     FeFejOj. 

Chromate   "     "     FeCr^O^. 

These  all  crystallize  in  isometric  octahedra,  and  are  in  every 
respect  very  similar  minerals.  The  salts  in  which  aluminium 
acts  as  an  acid  are  called  aluminates.  They  may  be  written 
as  salts  of  aluminic  acid,  HjAljO^,  but  there  are  other  alumin- 
ates known  having  a  smaller  proportion  of  alumina,  and  it  is 
much  more  convenient  to  express  the  composition  of  all  these 
aluminates  by  the  dualistic  method.  Thus,  there  are  known  to 
exist  (see  Bayer's  method  of  treating  bauxite,  next  chapter.) 



the  writing  of  which  formulae  by  the  rationalistic  method  would 
be  very  cumbersome. 

The  normal  or  neutral  salts  of  aluminium  as  a  base  may  be 
regarded  as  the  acid  with  its  hydrogen  replaced  by  alumin- 
ium.    Thus : 

Acid.  Salt. 

3HCI  AlCls 

3QH,0,  AlCQHsO,), 

3H,S0t  A1,(S0J3 

HaPjO^  AIP2O4 

Aluminium,  however,  has  a  great  tendency  to  form  basic 
salts  when  these  neutral  salts  are  put  in  contact  with  an  excess 
of  aluminium  or  alumina.  It  is  most  convenient  to  write  the 
formulae  of  these  by  the  dualistic  method.     Thus  we  have : 

Normal  sulphate,  AI2O3.3SO3.16HJO.  Basic  sulphate,  2AI2O3.SO3.10H2O. 

Normal  acetate,    AI2O3.6C2H2O.  Basic  acetate,     Al20s.2C2H.^0.2H20. 

While  the  writer  has  no  intention  of  going  back  to  the 
duaHstic  theories  which  such  formulae  were  first  used  to  repre- 
sent, yet  he  takes  the  liberty  of  using  these  formulas  to  represent 
the  empirical  composition  of  these  salts,  because  of  their  con- 
venience, and  without  attaching  to  them  any  theories  as  to  the 
internal  structure  of  the  molecules. 

General  methods  of  formation  and  properties. — Hydrated  alu- 
mina, which  has  not  been  too  strongly  heated,  dissolves  in 
strong  acids,  forming  salts  which  are  mostly  soluble  in  water. 
In  the  feebler  acids  and  in  all  organic  acids  it  is  completely  in- 
soluble. The  salts  of  these  latter  acids  are  formed  best  by  de- 
composing solution  of  aluminium  sulphate  with  the  barium  or 
lead  salt  of  the  acid  in  question.  Most  aluminium  salts  are 
soluble  in  water  and  rather  difficult  to  crystallize :  the  few  in- 
soluble salts  are  white,  gelatinous,  and   similar  to  the  hydrate 


in  appearance.  In  the  neutral  salts  the  acid  is  loosely  held, 
for  their  solution  strongly  reddens  litmus  paper  and  their  action 
is  as  if  part  of  the  acid  were  free  in  the  salt.  For  instance,  a 
solution  of  alum  attacks  iron  giving  ofi  hydrogen,  a  soluble 
basic  salt  of  aluminium  being  formed  as  well  as  sulphate  of 
iron.  The  neutral  salts  of  volatile  acids  give  ofif  acid  simply  by 
boiling  their  solutions,  basic  salts  being  formed.  An  aqueous 
solution  of  aluminium  chloride  loses  its  acid  almost  completely 
on  evaporation.  Gentle  ignition  is  sufficient  in  most  cases  to 
completely  decompose  aluminium  salts.  Hydrated  alumina 
dissolves  easily  in  caustic  alkali,  forming  soluble  aluminates ; 
with  baryta  two  aluminates  are  known,  one  soluble,  the  other 
not ;  all  other  known  aluminates  are  insoluble. 

Chemical  reactions. — Neutral  solutions  of  aluminium  salts 
react  as  follows  with  the  common  reagents : 

Hydrogen  sulphide  produces  no  precipitate. 

Ammonium  sulphide  precipitates  aluminium  hydrate  with 
separation  of  free  sulphur. 

Caustic  potash  or  soda  precipitates  aluminium  hydrate,  solu- 
ble in  excess. 

Aqua  ammonia  precipitates  aluminium  hydrate  insoluble  in 
excess,  especially  in  presence  of  ammoniacal  salts. 

Alkaline  carbonates  precipitate  aluminium  hydrate  insoluble 
in  excess. 

Sodium  phosphate  precipitates  white  gelatinous  aluminium 
phosphate,  easily  soluble  in  acids  or  alkalies. 

Before  the  blowpipe  most  aluminium  compounds  are  infusible 
or  are  quickly  converted  into  infusible  alumina.  In  the  light- 
colored,  infusible  compounds,  the  aluminium  may  be  recognized 
by  giving  a  beautiful,  enamel-like  blue  color  (Thenard's  blue) 
when  moistened  with  dilute  solution  of  cobalt  nitrate  and 
ignited  in  a  pure  oxidizing  flame.  Light-colored  fusible  com- 
pounds will  also  give  the  same  reaction,  but  in  them  the  ab- 
sence of  silica,  boric  and  phosphoric  acids  must  be  proven  by 
other  tests  before  the  presence  of  aluminium  can  be  asserted 
with  certainty. 

i  i  2  aluminium. 

Aluminium  Oxide. 

Commonly  called  alumina.  Composition  Al^Oj,  and  contains 
52.95  per  cent,  of  aluminium  when  perfectly  pure.  Colorless 
corundum  is  a  natural  pure  alumina,  in  which  state  it  is  infusible 
at  ordinary  furnace  heats,  insoluble  in  acids,  has  a  specific 
gravity  of  4,  and  is  almost  as  hard  as  the  diamond.  To  get 
this  into  solution  it  must  be  first  fused  with  potassium  hydrate 
or  bisulphate.  The  alumina  made  by  igniting  aluminium  hy- 
drate or  sulphate  is  a  white  powder,  easily  soluble  in  acids  if 
the  ignition  has  been  gentle,  but  becoming  almost  insoluble  if 
the  heat  has  been  raised  to  whiteness.  The  specific  gravity  of 
this  ignited  alumina  also  varies  with  the  temperature  to  which 
it  has  been  raised;  if  simply  to  red  heat,  it  is  3.75  ;  if  to  bright 
redness,  3.8;  and  if  to  whiteness,  3.9.  In  the  last  case  it  ac- 
quires almost  .the  hardness  of  corundum.  It  can  be  melted  to  a 
clear,  limpid  liquid  in  the  oxyhydrogen  blow-pipe ;  after  cool- 
ing it  forms  a  clear  glass,  often  crystallized.  Small  artificial 
crystals  of  alumina,  exactly  similar  to  the  natural  ones,  have 
been  obtained  by  dissolving  powdered  alumina  in  fused  boric 
oxide  and  then  volatilizing  the  latter  by  an  intense  heat. 
Fluorine  gas  acts  energetically  on  powdered  alumina.  As 
soon  as  it  comes  in  contact,  the  whole  mass  becomes  incandes- 
cent, forming  a  fluoride  and  disengaging  oxygen.     The  reaction 

A\A  +  6F  =  2AIF3  +  30. 

disengages  i,ioo  calories  of  heat  per  kilogramme  of  fluorine 
acting.  Gaseous  chlorine  does  not  act  on  it  even  at  redness, 
but  if  carbon  is  present  at  the  same  time  aluminium  chloride  is 
formed.  Similarly,  although  neither  carbon  nor  sulphur,  alone 
or  mixed  together,  acts  on  alumina,  carbon  bisulphide  converts 
it  into  aluminium  sulphide. 

The  preparation  of  alumina  for  commercial  purposes  is  de- 
scribed at  length  in  the  next  chapter. 

properties  of  aluminium  compounds.  ii 3 

Aluminium  Hydrates. 

There  are  three  natural  hydrates  of  aluminium,  which  may- 
be briefly  described  as  follows : 

Diaspore,  formula  AI2O3.H2O  or  Al202.(OH)j,  containing  85 
per  cent,  of  alumina,  occurs  in  crystalline  masses  as  hard  as 
quartz,  with  a  specific  gravity  of  3.4.  Bauxite,  approximately 
of  the  formula  AI2O3.2H2O  or  Al20.(OH)4,  with  the  aluminium 
replaced  by  variable  quantities  of  iron.  If  perfectly  pure,  it 
would  contain  74  per  cent,  of  alumina.  Hydrochloric  acid  re- 
removes  from  it  only  the  iron ;  heated  with  moderately  dilute 
sulphuric  acid  it  gives  up  its  alumina;  a  concentrated  alkaline 
solution  also  dissolves  the  alumina.  Calcined  with  sodium 
carbonate  it  forms  sodium  aluminate  without  melting.  Gibbsite, 
formula  AI2O3.3H2O  or  Al2(OH)6,  containing,  when  pure  sixty- 
five  per  cent,  of  alumina,  is  a  mineral  generally  stalactitic, 
white,  and  with  a  specific  gravity  of  2.4.  It  loses  two-thirds  of 
its  water  at  300°  and  the  rest  at  redness. 

The  artificial  hydrates  are  of  two  kinds,  the  soluble  and  in- 
soluble modifications.  The  latter  is  the  common  hydrate,  such 
as  is  obtained  by  adding  ammonia  to  a  solution  containing  alu- 
minium. The  precipitate  is  pure  white,  very  voluminous,  and 
can  be  washed  free  from  the  salts  with  which  it  was  precipi- 
tated only  with  great  difficulty.  Its  composition  is  Al2(OH)6, 
corresponding  to  the  mineral  gibbsite.  It  is  insoluble  in  water, 
but  easily  soluble  in  dilute  acids  or  alkali  solutions.  It  dis- 
solves in  small  quantity  in  ammonia,  but  the  presence  of  am- 
monia salts  counteracts  this  action.  When  dissolved  in  caustic 
potash  or  soda  the  addition  of  ammoniacal  salts  reprecipitates  it. 
It  loses  its  water  on  heating,  in  the  same  manner  as  gibbsite. 
Many  other  properties  of  this  hydrate,  and  its  manufacture  on 
a  large  scale,  are  given  in  the  next  chapter.  The  soluble  modi- 
fication can  only  be  made  by  complicated  processes,  too  long 
to  be  described  here,  and  is  principally  of  use  in  the  dyeing 
industries ;  a  full  description  can  be  found  in  any  good  chemi- 
cal dictionary. 

114  aluminium. 


Potassium  aluminate. — Formula  KjAljO^,  crystallizes  with 
three  molecules  of  water,  the  crystals  containing  forty  per  cent, 
alumina,  37.5  per  cent,  potassa  and  21.5  per  cent,  of  water.  It 
is  formed  when  precipitated  alumina  is  dissolved  in  caustic 
potash,  or  by  melting  together  alumina  and  caustic  potash  in  a 
silver  dish  and  dissolving  in  water.  If  the  solution  is  evapo- 
rated in  vacuo,  brilliant  hard  crystals  separate  out.  They  are 
soluble  in  water  but  insoluble  in  alcohol. 

Sodium  aluminate  has  not  been  obtained  crystallized.  Ob- 
tained in  solution  by  dissolving  alumina  in  caustic  soda  or  by 
fusing  alumina  with  caustic  soda  or  sodium  carbonate  and  dis- 
solving in  water.  If  single  equivalents  of  carbonate  of  soda 
and  alumina  are  used,  the  aluminate  seems  to  have  the  com- 
position NajAljOi)  if  an  excess  of  soda  is  used,  the  solution 
appears  to  contain  Al2(0Na)e,  or  AljOj.sNajO.  Dr.  Bayer 
thinks  that  Al203.2Na20  and  Al203.6Na20  are  also  possible  in 
solution.  If  a  solution  of  sodium  aluminate  is  concentrated  to 
20°  or  30°  B.,  alumina  separates  out;  if  carbonic  acid  gas  is 
passed  through  it,  aluminium  hydrate  is  precipitated.  For  a 
description  of  its'  manufacture  on  a  large  scale,  see  next 

Barium  aluminate. — Formula  BaAl^Oi.  Deville  prepared  it 
by  calcining  a  mixture  of  nitrate  or  carbonate  of  barium  with  • 
an  excess  of  alumina,  or  by  precipitating  sulphate  of  aluminium 
in  solution  by  baryta  water  in  excess.  The  aluminate  is  solu- 
ble in  about  ten  times  its  weight  of  water  and  crystallizes  out 
on  addition  of  alcohol.  The  crystals  contain  four  molecules  of 
water.  Gaudin  obtained  it  by  passing  steam  over  a  mixture  of 
alumina  and  barium  chloride,  or  of  alumina,  barium  sulphate, 
and  carbon,  at  a  red  heat.  Tedesco  claimed  that  by  heating 
to  redness  a  mixture  of  alumina,  barium  sulphate,  and  carbon, 
barium  aluminate  was  extracted  from  the  residue  by  washing 
with  water.  He  utilized  this  reaction  further  by  adding  solu- 
tion of  alkaline  sulphate,  barium  sulphate  being  precipitated 


(which  was  used  over),  while  alkaline  aluminate  remained  in 

Calcium,  aluminate. — Lime  water  precipitates  completely  a 
solution  of  potassium  or  sodium  aluminate,  insoluble  gelatinous 
calcium  aluminate  being  formed,  of  the  formula  A]2(06Ca3)  or' 
AljOs.sCaO.     At  a  red  heat  it  melts  to  a  glass,  which,  treated 
after  cooling  with  boiling  solution  of  boric  acid,  affords  a  com- 
pound appearing  to   contain  aAljOj-SCaO.     (Tissier.)     Lime 
water  is  also  completely  precipitated  by  hydrated  alumina,  the-^^ 
compound  formed  having  the  composition  CaAljOi  or  AI2O3.-- 
CaO.     Also,  by   igniting  at  a  high  temperature  an  intimate 
mixture  of   equal  parts  of   alumina  and  chalk,  Deville  obtained^ 
a  fused  compound  corresponding  to  the  formfila  CaAljO^. 

Zinc  aluminate  occurs  in  nature  as  the  mineral  Gahnit^, 
formula  ZnALOi.  Berzelius  has  remarked  that  when  a  solution 
of  zinc  oxide  in  ammonia  and  a  saturated  solution  of  alumina 
in  caustic  potash  are  mixed,  a  compound  of  the  two  oxides  is 
precipitated,  which  is  redissolved  by  an  excess  of  either  alkali. 

Copper  aluminate. — On  precipitating  a  dilute  solution  of 
sodium  aluminate  with  an  ammoniacal  solution  of  copper  sul- 
phate, the  clear  solution  remaining  contained  neither  copper 
nor  aluminium.  Whether  the  precipitate  contained  these  com- 
bined as  an  aluminate  I  did  not  determine. 

Magnesium  aluminate  occurs  in  nature  as  Spinel;  iron 
aluminate  as  Hercynite;  beryllium  aluminate  as  Chrysoberyl. 
The  first  mentioned  has  been  lately  proven  to  exist  in  small 
quantities  in  crystallized  blast-furnace  slags.*  Ebelman  has 
also  prepared  it  in  small  crystals  by  dissolving  alumina  and 
magnesia  in  fused  boric  oxide  and  driving  off  some  of  the 
solvent  by  intense  heat. 

Aluminium  Chloride. 

Formula  AICI3,  contains  20.2  per  cent,  of  aluminium.  The 
commercial  chloride  is  often  yellow  or  even  red  from  the  pres- 
ence of  iron,  but  the  pure  salt  is  quite  white.     It  absorbs  water 

*  P.  W.  Shimer.    Journal  Am.  Chemical  Soc,  1894,  p.  501. 


very  rapidly  from  the  air.  It  usually  sublimes  without  melting, 
■especially  when  in  small  quantity,  but  if  a  large  mass  is  rapidly 
ieated,  it  may  melt  and  even  boil,  but  its  melting  point  is  very 
close  to  its  boiling  point.  Friedel  and  Crafts  have  determined 
the  melting  point  as  178°,  boiling  point  183°.  When  sublimed 
it  deposits  in  brilliant,  hexagonal  crystals.  A  current  of  steam 
rapidly  decomposes  it  into  alumina  and  hydrochloric  acid. 
Oxygen  disengages  chlorine  from  it  at  redness,  but  decomposes 
it  incompletely.  Potassium  or  sodium  decomposes  it  ex- 
plosively, the  action  commencing  below  redness.  Anhydrous 
sulphuric  acid  converts  it  into  aluminium  sulphate.  Alumin- 
ium chloride  combines  with  many  other  chlorides,  forming  the 
double  salts. 

On  dissolving  this  salt  in  water,  or  by  dissolving  alumina  in 
hydrochloric  acid,  a  solution  is  obtained  which  on  evaporation 
deposits  crystals  having  the  formula  AICI3.6H2O.  If  these 
crystals  are  heated,  they  decompose,  losing  both  water  and 
acid  and  leaving  alumina.  Thus  it  is  not  possible  to  obtain 
anhydrous  aluminium  chloride  by  evaporating  its  solution,  and 
the  anhydrous  salt  must  be  made  by  other  methods,  detailed  at 
length  in  the  next  chapter. 

Aluminium-Sodium  Chloride. 

formula  AlClj.NaCl  contains  14  per  cent,  of  aluminium. 
The  commercial  salt  is  often  yellow  or  brown  from  the  presence 
,of  ferric  chloride,  but  the  pure  salt  is  perfectly  white.  Its  melt- 
ing point  has  been  generally  stated  to  be  180°,  but  Mr.  Baker, 
<chemis.t  for  the  Aluminium  Company  of  London,  states  that 
-when  .the  absolutely  pure  salt  is  warmed  it  melts  at  125°  to 
130°.  Xhat  chemists  should  for  thirty  years  have  made  an 
.error  of  this  magnitude  seems  almost  incredible,  and  it  would 
be  satisfactory  if  Mr.  Baker  would  advance  some  further  in- 
formation than  the  bare  statement  above.  This  salt  volatilizes 
at  a  red  heat  without  decomposition.  It  is  less  deliquescent  in 
the  air  .than  aluminium  chloride,  and  for  this  reason  is  much 
icagier  .to  handle  on  a  large  scale.     It  is  recently  stated  that  the 


absolutely  pure  salt  deteriorates  less  than  the  impure  salt  in  the 
air,  and  the  inference  is  drawn  that  perhaps  the  greater  deli- 
quescence of  the  impure  salt  is  due  to  the  iron  chlorides  pres- 
ent. Its  solution  in  water  behaves  similarly  to  that  of  alumin- 
ium chloride ;  it  cannot  be  evaporated  to  dryness  without 
decomposition,  the  residue  consisting  of  alumina  and  sodiun:i 

The  manufacture  of  this  double  salt  on  a  large  scale  is  de- 
scribed in  the  next  chapter.  It  may  be  prepared  in  the  labora- 
tory by  melting  a  mixture  of  the  two  component  salts  in  the 
proper  proportions.  A  similar  salt  with  potassium  chloride 
may  be  prepared  by  exactly  analogous  reactions. 

Aluminium-Phosphorus  Chloride. 

Formula  2AICI3.PCI5,  contains  9  per  cent,  of  aluminium.  It 
is  a  white  salt,  easily  fusible,  volatilizes  only  about  400°  and 
sublimes  slowly,  fumes  in  the  air  and  is  decomposed  by  water. 
Produced  by  heating  the  two  chlorides  together  or  by  passing 
vapor  of  phosphorus  perchloride  over  alumina  heated  to  redness. 

Aluminium-Sulphur  Chloride. 

Formula  2AICI3.SCI4,  contains  12.2  per  cent,  of  aluminium. 
It  forms  a  yellow  crystalline  mass,  fuses  at  100°,  may  be  dis- 
tilled without  change,  and  is  decomposed  by  water.  May  be 
obtained  by  distilling  a  mixture  of  aluminium  chloride  and 
ordinary  sulphur  chloride,  SClj. 

Aluminium-Selenium  Chloride. 

Formula  2AlCl3.SeCl4.  Obtained  by  heating  the  separate 
chlorides  together  in  a  sealed  tube,  when  on  careful  distillation 
the  less  volatile  double  chloride  remains.  It  is  a  yellow  mass, 
melting  at  100°  and  decomposed  by  water. 

Aluminium-Ammonium  Chloride. 

Formula  2AICI3.3NH3.  Solid  aluminium  chloride  absorbs 
ammonia  in  large  quantity,  the  heat  developed  liquefying  the 


resulting  compound.      It  may  be    sublimed  in  a  current  of 
hydrogen,  but  loses  ammonia  thereby  and  becomes  2AICI3.NH3. 


Formed  by  subliming  aluminium  chloride  in  a  current  of 
hydrogen  sulphide.  A  current  of  hydrogen  removes  the  ex- 
cess of  the  gas  used,  leaving  on  sublimation  fine  colorless 
crystals.  In  air  it  deliquesces  rapidly  and  loses  hydrogen 


Apparently  of  the  formula  6AICI3.PH3.  If  phosphuretted 
hydrogen  is  passed  over  cold  aluminium  chloride  very  little  is 
absorbed,  but  at  its  subliming  point  it  absorbs  a  large  quantity, 
the  combination  subliming  and  depositing  in  crystals.  It  is 
decomposed  by  water  or  ammonium  hydrate,  disengaging 
hydrogen  phosphide. 

Aluminium  Bromide. 

Formula  AlBrg,  containing  lo.i  per  cent,  of  aluminium.  It 
is  colorless,  crystalline,  melts  at  93°  to  a  clear  fluid  which  boils 
at  260°.  It  is  still  more  deliquescent  than  aluminium  chloride. 
At  a  red  heat  in  contact  with  dry  oxygen,  it  evolves  bromine 
and  forms  alumina ;  it  is  also  decomposed  slowly  by  the  oxy- 
gen of  the  air.  It  dissolves  easily  in  carbon  bi-sulphide,  the 
solution  fuming  strongly  in  the  air.  It  reacts  violently  with 
water,  the  solution  on  evaporation  depositing  the  compound 
AlBr3.6H20.  The  same  result  is  attained  by  dissolving  alumina 
in  hydrobromic  acid  and  evaporating.  This  hydrated  chloride 
is  decomposed  by  heat,  leaving  alumina.  The  specific  gravity 
of  solid  aluminium  bromide  is  2.5. 

This  compound  is  obtained  by  heating  aluminium  and  bro- 
mine together  to  redness,  or  by  passing  bromine  vapor  over  a 
mixture  of  alumina  and  carbon  at  bright  redness. 

Aluminium  Iodide. 
Formula  AII3,  containing  6.6  per  cent,  of  aluminium.     This 


compound  is  a  white  solid,  fusible  at  125°,  and  boils  at  350°. 
It  dissolves  easily  in  carbon  bisulphide,  the  warm  saturated 
solution  depositing  it  in  crystals  on  cooling.  It  dissolves  also 
in  alcohol  and  ether.  Its  behavior  towards  water  is  exactly 
analogous  to  that  of  aluminium  bromide.  It  is  prepared  by 
heating  iodine  and  aluminium  together,  with  special  precau- 
tions to  avoid  explosion. 

Aluminium  Fluoride. 

Formula  AIF3,  containing  32.7  per  cent,  of  aluminium.  It 
is  sometimes  obtained  in  crystals  which  are  colorless  and 
slightly  phosphorescent.  They  are  insoluble  in  acids,  even  in 
boiling  sulphuric,  and  boiling  solution  of  potash  scarcely  at- 
tacks them ;  they  can  only  be  decomposed  by  fusion  with 
sodium  carbonate  at  a  bright  red  heat.  Melted  with  boric 
acid,  aluminium  fluoride  forms  crystals  of  aluminium  borate. 
L.  Grabau  describes  the  aluminium  fluoride  which  he  obtains 
in  his  process  as  being  a  white  powder,  unalterable  in  air, 
unaffected  by  keeping,  insoluble  in  water,  infusible  at  redness, 
but  volatilizing  at  a  higher  temperature. 

Deville  first  produced  this  compound  by  acting  on  alumin- 
ium with  silicon  fluoride  at  a  red  heat.  He  afterwards  obtained 
it  by  moistening  pure  calcined  alumina  with  hydrofluoric 
acid,  drying  and  introducing  into  a  tube  made  of  gas  carbon, 
protected  by  a  refractory  envelope.  The  tube  was  heated  to 
bright  redness,  a  current  of  hydrogen  passing  through  mean- 
while to  facilitate  the  volatilization  of  the  fluoride.  Brunner 
demonstrated  that  aluminium  fluoride  is  formed  and  volatilized 
when  hydrofluoric  acid  gas  is  passed  over  red-hot  alumina. 
Finally,  if  a  mixture  of  fluorspar  and  alumina  is  placed  in  car- 
bon boats,  put  into  a  carbon  tube,  suitably  protected,  heated  to 
whiteness  and  gaseous  hydrofluoric  acid  passed  over  it,  alu- 
minium fluoride  will  volatilize  and  condense  in  the  cooler  part 
of  the  tube  in  fine  cubical  crystals,  while  calcium  fluoride  re- 
mains in  the  boats. 

i20  aluminium. 

Aluminium  Fluorhydrate. 
When  calcined  alumina  or  kaolin  is  treated  with  hydrofluoric 
acid,  alumina  being  in  excess,  soluble  fluorhydrate  of  alumin- 
ium is  formed,  which  deposits  on  evaporating  the  solution.  It 
has  the  formula  2AIF3.5H2O,  and  easily  loses  its  water  when 

Aluminium-Hydrogen  Fluoride. 

If  to  a  strongly  acid  solution  of  alumina  in  hydrofluoric  acid 
alcohol  is  added,  an  oily  material  separates  out  and  crystallizes, 
having  the  formula  3AIF3.2HF.5H2O.  If  the  acid  solution  is 
simply  evaporated,  acid  fumes  escape  and  a  crystalline  mass 
remains  which,  washed  with  boiling  water  and  dried,  has  the 
formula  4AIF3.HF.10H2O.  On  heating  these  compounds  to 
400°  or  500°  in  a  current  of  hydrogen,  pure  amorphous  alu- 
minium fluoride  remains.  The  acid  solution  of  alumina  first 
used  seems  to  contain  an  acid  of  the  composition  AIF3.3HF, 
which  is  capable  of  forming  salts  with  other  bases.  Thus,  if 
this  solution  is  neutralized  with  a  solution  of  soda,  a  precipitate 
of  artificial  cryolite,  AlFs.sNaF,  falls.  The  similar  potash 
compound  is  formed  in  the  same  way. 

Aluminium-Sodium  Fluoride. 

Formula  AlFs.sNaF,  containing  12.85  P^r  cent,  of  aluminium, 
occurs  native  as  cryolite,  a  white  mineral  with  a  waxy  appear- 
ance, as  hard  as  calcite,  specific  gravity  2.9,  melting  below 
redness  and  on  cooling  looking  like  opaque,  milky  glass.  If 
kept  melted  in  moist  air,  or  in  a  current  of  steam,  it  loses 
hydrofluoric  acid  and  sodium  fluoride  and  leaves  a  residue  of 
pure  alumina.  When  melted  it  is  decomposable  by  an  electric 
current  or  by  sodium  or  magnesium.  It  is  insoluble  in  water, 
unattacked  by  hydrochloric  but  decomposed  by  hot  sulphuric 
acid.  The  native  mineral  is  contaminated  with  ferrous  carbon- 
ate, silica,  phosphoric  and  vanadic  acids.  An  extended  de- 
scription of  its  utilization,  manufacture,  etc.,  will  be  found  in 
the  next  chapter. 


A  native  compound  having  the  formula  sAlFj.jNaF  is  snow- 
white,  very  similar  to  cryolite  in  appearance  and  properties, 
except  that  it  crystallizes  in  a  different  form  and  is  more 
fusible.  It  is  called  Chiolite.  The  mineral  Pachnolite  is  also 
similar,  except  that  part  of  the  sodium  is  displaced  by  calcium. 

Aluminium  Sulphide. 

Formula  AI2S3,  containing  36  per  cent,  of  aluminium.  The 
pure  salt  is  light  yellow  in  color  and  melts  at  a  high  tempera- 
ture. In  damp  air  it  swells  up  and  disengages  hydrogen  sul- 
phide, forming  a  grayish  white  powder ;  it  decomposes  water 
very  actively,  forming  hydrogen  sulphide  and  ordinary  gela- 
tinous aluminium  hydrate.  Steam  decomposes  it  easily,  at  red 
heat  forming  amorphous  alumina,  which  is  translucent  and  very 
hard.  Gaseous  hydrochloric  acid  transforms  it  into  aluminium 
chloride.  Elements  having  a  strong  affinity  for  sulphur  reduce 
it,  setting  free  aluminium,  but  it  is  doubtful  if  hydrogen  or 
carburetted  hydrogen  has  this  efifect. 

It  may  be  formed  by  throwing  sulphur  into  red-hot  alumin- 
ium, or  by  passing  sulphur  vapor  over  red-hot  aluminium. 
Traces  only  of  aluminium  sulphide  are  formed  by  passing 
hydrogen  sulphide  over  ignited  alumina,  but  carbon-bisulphide 
vapor  readily  produces  this  reaction.  For  details  of  its  forma- 
tion see  next  chapter. 

Double  sulphides  of  aluminium  and  sodium  or  potassium,, 
similar  in  composition  to  the  double  chlorides,  may  be  made 
by  melting  the  two  sulphides  together,  or,  more  easily,  by  add- 
ing sodium  or  potassium  carbonate  to  the  ignited  alumina 
which  is  in  process  of  conversion  into  sulphide.  These  salts 
are  easily  fusible  and  nearly  unchangeable  in  the  air,  but  a 
more  detailed  description  of  them  is  wanting.  They  are  said 
to  be  quite  suitable  for  electrolytic  decomposition.  (See 
Bucherer's  electrolytic  process.) 

Aluminium  sulphide  has  recently  come  into  use  in  chemical 
laboratories  as  a  very  convenient  means  of  generating  hydrogen 
sulphide.     A  London  chemical  firm  manufactures  it  by  stirring 


aluminium  into  molten  sulphide  of  lead ;  the  lead  separating 
out  sinks  to  the  bottom,  while  the  aluminium  sulphide  floats. 
The  sulphide  is  sold  at  $0.6o  per  pound,  and  is  said  to  gen- 
erate the  gas  as  cheaply  as  by  the  ordinary  methods. 

Aluminium  Selenide. 

When  aluminium  is  heated  in  selenium  vapor,  the  two  ele- 
ments combine  with  incandescence,  producing  a  black  powder. 
In  the  air  this  powder  evolves  the  odor  of  hydrogen  selenide ; 
in  contact  with  water  it  disengages  that  gas  abundantly,  and 
furnishes  a  red  deposit  of  selenium  along  with  aluminium 
hydrate.  When  a  solution  of  an  aluminium  salt  is  treated  with 
an  alkaline  poly-selenide,  a  flesh-colored  precipitate  falls,  the 
composition  of  which  is  not  known,  which  is  decomposed  at 
redness,  leaving  aluminium. 

Aluminium  Borides. 

AIB2,  containing  55.1  per  cent,  of  aluminium,  was  first  ob- 
tained by  Deville  and  Wohler  by  heating  boron  in  contact  with 
aluminium,  or  by  reducing  boric  acid  with  the  latter  metal,  the 
action  not  being  long  continued.  Also,  if  a  current  of  boron 
trichloride  with  carbonic  oxide  is  passed  over  aluminium  in 
boats  in  a  tube  heated  to  redness,  aluminium  chloride  volatil- 
izes and  there  remains  in  the  boats  a  crystalline  mass,  cleav- 
able,  and  covered  with  large  hexagonal  plates  of  a  high  metal-  ' 
lie  lustre.  To  remove  the  aluminium  present  in  excess,  the 
mass  is  treated  with  hydrochloric  acid  and  then  with  caustic 
soda.  The  final  residue  is  composed  of  hexagonal  tablets,  very 
thin  but  perfectly  opaque,  of  about  the  color  of  copper.  These 
crystals  do  not  burn  in  the  air,  even  if  heated  to  redness,  but 
their  color  changes  to  dark-gray.  They  burn  in  a  current  of 
chlorine,  giving  chlorides  of  the  two  elements  contained  in 
them.  They  dissolve  slowly  in  concentrated  hydrochloric  acid 
or  in  solution  of  caustic  soda ;  nitric  acid,  moderately  concen- 
trated, attacks  them  quickly. 

AlBs,  containing  45   per  cent,  of  aluminium,  has  been  ob- 


tained  by  Hampe  by  heating  aluminium  with  boric  acid  for 
three  hours  at  a  high  temperature,  carbon  being  carefully  kept 
away.  On  cooling  very  slowly,  the  upper  part  of  the  fusion  is 
composed  of  aluminium  borate,  the  centre  is  of  very  hard 
alumina  containing  a  few  black  crystals  of  aluminium  boride, 
while  at  the  bottom  is  a  button  of  aluminium  also  containing 
these  crystals.  To  free  these  crystals,  the  aluminium  is  dis- 
solved by  hydrochloric  acid.  These  crystals  are  the  compound 
sought  for,  and  contain  no  other  impurity  than  a  little  alumina, 
which  can  be  removed  by  boihng  sulphuric  acid.  These  puri- 
fied crystals  are  black,  but  are  thin  enough  to  show  a  dark-red 
by  transmitted  light.  Their  specific  gravity  is  2.5,  they  are 
harder  than  corundum,  but  are  scratched  by  the  diamond. 
Oxygen  has  no  action  on  them  at  a  high  temperature,  solution 
of  caustic  potash  or  hydrochloric  acid  does  not  attack  them, 
boiling  sulphuric  acid  has  scarcely  any  action,  but  they  dissolve 
completely  in  warm,  concentrated  nitric  acid. 

If  the  operation  by  which  this  product  is  made  is  conducted 
in  the  presence  of  carbon,  the  compound  formed  contains  less 
aluminium  and  also  some  carbon.  Its  composition  corresponds 
to  the  formula  Al3C2B«,  containing  about  12  per  cent,  of  alu- 
minium and  3.75  per  cent,  of  carbon.  The  crystals  of  this 
compound  are  yellow  and  as  brilliant  as  the  diamond.  Their 
specific  gravity  is  2.6,  hardness  between  that  of  corundum  and 
the  diamond.  They  are  not  attacked  by  oxygen,  even  at  a 
high  temperature;  hot  hydrochloric  or  sulphuric  acid  attacks 
them  only  superficially,  concentrated  nitric  acid  dissolves  them 
slowly  but  completely.  They  resist  boiling  solution  of  caustic 
potash  or  fused  nitre,  but  take  fire  in  fused  caustic  potash  or 
chromate  of  lead. 

Aluminium  and  Carbon. 

Deviile  stated  that  he  was  unable  to  combine  carbon  with 
aluminium.  On  decomposing  carbon  tetrachloride  by  aluniin- 
ium,  ordinary  carbon  was  formed,  while  the  aluminium  remain- 
ing was   unchanged.     The   Cowles   Company  obtain  in   their 


electric  furnace,  when  reducing  a  mixture  of  alumina  and  car- 
bon alone,  a  yellow,  crystalline  substance  which  was  exhibited 
by  Dr.  T.  Sterry  Hunt,*  as  an  alloy  of  aluminium  and  carbon,, 
but  that  this  is  the  case  is  not  yet  accepted  as  certain. 

On  dissolving  impure  aluminium  in  solution  of  caustic  pot- 
ash, a  black  residue  was  obtained  which  behaved,  when  filtered' 
out  and  dried,  partly  like  amorphous  carbon.  I  have  heard 
it  stated  that  molten  aluminium  does  not  dissolve  appreciable- 
quantities  of  carbon,  and  that  its  properties  are  affected  con- 
siderably thereby;  but  I  am  not  able  to  give  any  further  light 
on  the  subject  than  the  above  experiment,  which  seemed  to- 
show  considerable  carbon  in  an  impure  metal.  This  is  a  sub- 
ject which  needs  thorough  investigation. 

Since  the  observation  just  given  was  made,  in  1890,  the  fact 
that  this  residue  does  contain  amorphous  carbon  has  been  es- 
tablished by  Le  Verrier  (see  p.  57),  who  has  also  confirmed 
Hunt's  statements  as  to  an  aluminium  carbide.  Le  Verrier 
states  I  that  up  to  his  own  experiments  this  compound  was 
unknown,  but  he  must  have  been  ignorant  of  Hunt's  observa- 
tions. The  method  used  by  Le  Verrier  was  as  follows:  Little 
boats  of  carbon  were  filled  with  aluminium,  put  into  a  carbon 
tube  through  which  a  current  of  hydrogen  was  passed,  and 
heated  in  the  electric  furnace.  After  cooling,  the  aluminium 
was  of  a  grey  color,  and  on  breaking  it  was  seen  to  be  strewn 
with  brilliant  fine-yellow  crystals.  To  separate  these  out,  the 
aluminium  is  dissolved  by  concentrated  hydrochloric  acid,  sur- 
rounding the  vessel  with  ice  to  keep  the  temperature  low.  The 
residue  is  washed  with  ice-cold  water.  This  whole  operation 
must  be  conducted  as  quickly  as  possible,  since  the  carbide  is 
attacked  by  water. 

The  carbide  thus  prepared  has  a  specific  gravity,  taken  in 
benzine,  of  2.36.  It  is  decomposed  in  the  highest  heat  of  an 
electric  furnace,  attacked  by  chlorine  at  a  red-heat,  but  only 

♦Halifax  Meeting,  Am.  Ins.  Mining  Engineers,  Sept.  i6,  1885. 
tComptes  Rendus,  July,  1894,  p.  16. 


superficially  by  oxygen,  since  the  layer  of  alumina  formed  pro- 
tects the  part  underneath.  Violently  attacked  by  sulphur  at 
that  temperature,  also  by  permanganate  of  potassium,  bichro- 
mate of  potassium,  chromic  acid  and  oxide  of  lead ;  potassium 
chlorate  has  no  action.  Caustic  potash  in  fusion  attacks  it  very 
energetically  at  about  300°.  It  slowly  decomposes  water  in 
the  cold  with  a  very  curious  result,  namely,  the  formation  of 
jnethane  gas,  according  to  the  reaction : 

QAl^  +  12H2O  =  aCH,  -f-  4A1(0H)3. 

An  analysis  of  these  crystals  gave  the  following  result : 

Aluminium.  Carbon. 

7448  23.5 

7.5.12  24.2 

74-7  24.7 

74.9  24.8 


(Required  by  the  formula  AI4C3.) 

75.4  24.6 

Aluminium  Nitride. 

Formula  AIN,  containing  66  per  cent,  of  aluminium,  is 
iormed  when  aluminium  is  heated  in  a  carbon  crucible  to  a 
high  temperature.  Mallet*  obtained  it  unexpectedly  when 
heating  aluminium  with  dry  sodium  carbonate  at  a  high  heat, 
lor  several  hours,  in  a  carbon  crucible.  The  aluminium  is  par- 
tially transformed  into  alumina,  some  sodium  vaporizes,  and 
some  carbon  is  deposited.  After  cooling,  there  are  found  on 
the  surface  of  the  button  little  yellow  crystals  and  amorphous 
drops,  to  recover  which  the  whole  is  treated  with  very  dilute 
hydrochloric  acid.  This  product  has  the  composition  AIN. 
"Calcined  in  the  air  it  slowly  loses  nitrogen  and  forms  alumina. 
It  decomposes  in  moist  air,  loses  its  transparency,  becomes  a 
lighter  yellow,  and  finally  only  alumina  remains,  the  nitrogen 

*Ann.  der  Chemie  u.  Pharmacie,  186,  p.  155. 


having  formed   ammonia.     Melted  with  caustic  potash  it  dis- 
engages ammonia  and  forms  potassium  aluminate. 

Aluminium  Sulphate. 

Anhydrous. — The  salt  obtained  by  drying  hydrated  alumin- 
ium sulphate  at  a  gentle  heat  has  the  formula  Al2(S04)3,  con- 
taining 15.8  per  cent,  of  aluminium,  and  of  a  specific  gravity 
of  2.67.  By  heating  this  salt  several  minutes  over  a  Bunsen 
burner  it  loses  almost  all  its  acid,  leaving  alumina.  Hydrogen 
likewise  decomposes  it  at  redness,  forming  water  and  sulphur 
dioxide  and  leaving  alumina  with  hardly  a  trace  of  acid. 
Melted  with  sulphur,  Violi  states  that  it  is  transformed  into 
aluminium  sulphide,  evolving  sulphurous  acid  gas.*  Hot 
hydrochloric  acid  in  excess  partly  converts  it  into  aluminium 

Hydrated. — This  is  the  ordinary  aluminium  sulphate;  its 
formula  is  Al2(S04)3.i6H20,  and  it  contains  8.0  per  cent,  of 
aluminium,  equal  to  14.5  per  cent,  of  alumina,  and  47  per  cent, 
of  water.  The  pure  salt  is  not  hygroscopic.  In  the  presence 
of  impurities  the  amount  of  water  increases  to  18  H2O  and  the 
salt  becomes  hygroscopic.  It  has  a  white,  crystalline  appear- 
ance, and  tastes  like  alum.  It  dissolves  freely  in  water,  from 
which  it  crystallizes  out  at  ordinary  temperatures  with  the 
above  formula ;  crystallized  out  at  a  low  temperature  it  retains 
27H2O,  or  one-half  as  much  again.  Water  dissolves  one-half 
its  weight  of  this  salt,  the  solution  reacting  strongly  acid ;  it  is 
almost  insoluble  in  alcohol.  At  a  gentle  heat  it  melts  in  its 
water  of  crystallization,  then  puffs  up  and  leaves  a  porous  mass 
of  anhydrous  sulphate  which  is  soluble  with  difficulty  in  water. 
If  heated  to  redness  it  leaves  only  alumina.  The  salt  with 
16H2O  has  a  specific  gravity  of  1.76;  it  is  the  salt  found  in 
fibrous  masses  in  solfataras,  its  mineralogical  name  being  Halo- 
trichite.  A  hydrated  sulphate  with  10H2O  is  formed  and  pre- 
cipitated when  alcohol  is  added  to  an  aqueous  solution  of  alu- 

*  Berichte  der  Deutschen  Chemischen  Gesellschaft,  X,  293. 


minium  sulphate.     On  heating  it  acts  similarly  to  the  other 
hydrated  sulphates. 

Basic. — On  precipitating  a  solution  of  aluminium  sulphate 
with  alkaline  hydrate  or  carbonate,  a  series  of  basic  salts  are 
formed.  On  precipitating  with  ammonia,  the  compound  formed 
has  the  formula  AljO3.SO3.9HjO,  corresponding  to  the  mineral 
Aluminite.  If  the  ammonia  is  in  insufficient  quantity  to  en- 
tirely precipitate  the  solution,  a  precipitate  is  very  slowly 
formed  having  the  formula  3AI2O3.2SO3.20H2O.  On  precipitat- 
ing a  cold  solution  of  alum  by  alkaline  carbonate  not  in  excess, 
a  precipitate  is  very  slowly  formed  having  the  formula  2A1203.- 
SO3.12H2O.  If  a  very  dilute  solution  of  acetate  of  alumina  is 
precipitated  by  adding  potassium  sulphate,  a  compound  de- 
posits very  slowly  having  the  formula  2AI2O3.SO3.10H2O.  Na- 
tive minerals  are  met  with  of  analogous  composition  to  these 
precipitates:  Felsobanyte,  2AI2O3.SO3.10H2O ;  Paraluminite, 
2AI2O3.SO3.ISH2O.  By  heating  a  concentrated  solution  of  alu- 
minium sulphate  with  aluminium  hydrate,  and  filtering  cold, 
the  solution  deposits  on  further  cooling  a  gummy  mass  having 
the  formula  Al203.2S03.;irH20.  On  washing  with  water  it  de- 
posits a  basic  salt  having  the  formula  AI2O3.SO3.  By  letting 
stand  a  very  dilute  solution  of  sulphuric  acid  completely  satu- 
rated with  aluminium  hydrate,  Rammelsberg  obtained  trans- 
parent crystals  having  the  formula  3AI2O3.4SO3.30H2O.  On 
boiling  a  solution  of  aluminium  sulphate  with  zinc,  Debray 
obtained  a  granular  precipitate  having  the  formula  5AI2O3.3SO3.- 
20H2O.  By  leaving  zinc  a  long  time  in  a  cold  solution  of  alu- 
minium sulphate,  a  gelatinous  precipitate  was  obtained  having 
the  formula  4AI2O3.3SO3.36H2O ;  the  same  compound  was 
formed  if  the  zinc  was  replaced  by  calcium  carbonate. 

The  manufacture  of  aluminium  sulphate  from  clay,  aluminous 
earths,  cryolite,  bauxite,  etc. ,  is  carried  on  industrially  on  a 
very  large  scale ;  descriptions  of  the  processes  used  may  be 
found  in  any  work  on  industrial  chemistry — they  are  too  foreign 
to  metallurgical  purposes  to  be  treated  of  here. 

128  aluminium. 


Under  this  name  are  included  a  number  of  double  salts  con- 
taining water,  crystallizing  in  octahedra  and  having  the  general 
formula  R2S04.R2(S04)3.24H20,  in  which  the  first  R  may  be 
potassium,  sodium,  rubidium,  caesum,  ammonium,  thallium  or 
even  organic  radicals ;  the  second  R  may  be  aluminium,  iron, 
manganese  or  chromium ;  the  acid  may  even  be  selenic,  chro- 
mic or  manganic,  instead  of  sulphuric.  We  will  briefly  describe 
the  most  important  alums  consisting  of  double  sulphates  of 
aluminium  and  another  metal,  remarking,  as  with  aluminium 
sulphate,  that  their  preparation  may  be  found  at  length  in  any 
chemical  treatise. 

Potash  Alum. 

Formula  K2S04.Al2(S04)3.24H20,  containing  10.7  per  cent,  of 
alumina  or  5.7  per  cent,  of  aluminium.  Dissolves  in  25  parts 
of  water  at  0°  and  in  two-sevenths  part  at  100°.  The  solution 
reacts  acid.  It  forms  colorless,  transparent  octahedrons,  insol- 
uble in  alcohol.  On  exposure  to  air  they  become  opaque, 
being  covered  with  a  white  coating,  which  is  said  not  to  be 
efflorescence — a  loss  of  water — but  to  be  caused  by  absorption 
of  ammonia  from  the  air.  The  crystals  melt  in  their  water  of 
<;rystallization,  but  lose  it  all  above  100°.  Heated  to  redness 
it  swells  up  strongly,  becomes  porous  and  friable,  giving  the 
product  called  calcined  alum;  at  whiteness  it  loses  a  large  part 
of  its  sulphuric  acid,  leaving  a  residue  of  potassium  sulphate  and 
alumina.  If  it  is  mixed  with  one-third  its  weight  of  carbon  and 
calcined,  the  residue  inflames  spontaneously  in  the  air.  If  a 
mixture  of  alumina  and  bisulphate  of  potassium  is  fused  and 
afterwards  washed  with  warm  water,  a  residue  is  obtained  of 
anhydrous  alum,  or  K2S04.Al2(S04)3.  The  mineral  Alunite  is 
a  basic  potash  alum,  K2S04.3(A1A-S0,).6H20. 

Ammonia  Alum. 

Formula  (NH0,SO4.Al2(SOl)s.24HjO,  containing  11.3  per 
■cent,  of  alumina  or  6.0  per  cent,  of  aluminium.     Dissolves  in 


20  parts  of  water  at  0°  and  in  one-fourth  part  at  100°.  When 
heated,  the  crystals  swell  up  strongly,  forming  a  porous  mass, 
losing  at  the  same  time  water  and  sulphurous  acid ;  if  the  tem- 
perature is  high  enough  there  remains  a  residue  of  pure  alu- 
mina. The  temperature  necessary  for  complete  decomposition 
is  higher  than  that  required  for  volatilizing  ammonium  sulphate 

Soda  Alum. 

Formula  Na2S04.Al2(S04)3.24H20,  containing  11. i  per  cent, 
of  alumina  or  5.9  per  cent,  of  aluminium.  Dissolves  in  an 
equal  weight  of  water  at  ordinary  temperatures.  The  crystals 
effloresce  and  fall  to  powder  in  the  air.  It  is  insoluble  in  abso- 
lute alcohol.  On  account  of  its  great  solubility  in  water  it 
cannot  be  separated  from  ferrous  sulphate  by  crystallization,  and 
therefore  it  is  either  contaminated  with  much  iron  or  else,  to 
be  obtained  pure,  special  expensive  methods  must  be  adopted. 
These  diflSculties  cause  the  manufacture  of  soda  alum  to  be  in- 
significant in  amount  when  compared  with  potash  alum. 

Aluminium-Metallic  Sulphates. 

Sulphate  of  aluminium  forms  double  sulphates  with  iron, 
manganese,  magnesium  and  zinc,  but  these  compounds  are  not 
analogous  to  the  alums.  They  are  extremely  soluble  in  water, 
do  not  crystallize  in  octahedrons  or  any  isometric  forms,  and 
their  composition  is  different  from  the  alums  in  the  amount  of 
water  of  crystallization.  It  has  heen  determined  that  the  double 
sulphates  with  manganese  and  zinc  contain  25  equivalents  of 
water,  which  would  permit  their  being  considered  as  combina- 
tions of  sulphate  of  aluminium,  Al2(S04)3.i8H20,  with  a  sul- 
phate of  the  magnesian  series  containing  seven  equivalents  of 
water,  as  ZnS04.7H20. 

Aluminium  Selenites. 

By  adding  a  solution  of  selenite  of  soda  to  one  of  sulphaite 
of  aluminium  maintained  in  excess,  an  amorphous,  voluminous 


precipitate  forms,  having  the  composition  4Al2O3.9SeO2.3H2O. 
This  substance  decomposes  on  being  heated,  leaving  alumina. 
If  varying  quantities  of  selenious  acid  are  added  to  this  first 
salt,  other  salts  of  the  formulas  Al2O3.3SeO2.7H2O,  2Al203.9Se02. 
12H2O,  Al2O3.6SeO2.SH2O,  are  formed.  These  are  mostly  in- 
soluble in  water  and  decompose  on  being  heated,  like  the  first. 

Aluminium  Nitrate. 

Formula  A1(N03)3.9H20  is  obtained  on  dissolving  aluminium 
hydrate  in  nitric  acid.  If  the  solution  is  evaporated  keeping  it 
strongly  acid,  it  deposits  on  cooling  voluminous  crystals  having 
the  formula  2Al(N03)3.isH20.  This  salt  is  deliquescent,  melts 
at  73°  and  gives  a  colorless  liquid  which,  on  cooling,  becomes 
crystalline.  It  is  soluble  in  water,  nitric  acid,  and  alcohol ;  on 
evaporating  these  solutions  it  is  obtained  as  a  sticky  mass.  It 
is  easily  decomposed  by  heat;  if  kept  at  100°  for  a  long  time 
it  loses  half  its  weight,  leaving  as  residue  a  soluble  salt  of  the 
formula  2AI2O3.3N2O5.3H2O.  Carried  to  140°,  this  residue 
loses  all  its  nitric  acid,  leaving  alumina.  On  this  property  is 
based  a  separation  of  alumina  from  lime  or  magnesia,  since  the 
nitrates  of  these  latter  bases  resist  the  action  of  heat  much 
better  than  aluminium  nitrate. 

Aluminium  Antimonate. 

Al203.3Sb205.isH20  can  be  prepared  by  double  decomposi- 
tion from  potassium  antimonate  and  a  soluble  aluminium  salt. 
It  deposits  from  solution  after  several  days'  standing  in  shin- 
ing, microscopic  crystals.  At  100°  it  loses  sHjO,  at  150°,  2^ 
H2O  more,  at  200°  it  retains  only  3H2O  and  becomes  incandes- 
cent.    Al2O3.Sb2O5.9H2O  has  been  also  described. 

Aluminium  Phosphates. 

The  normal  phosphate,  AIPO4,  is  obtained  as  a  white,  gelat- 
inous precipitate  when  a  neutral  aluminium  solution  is  treated 
with  sodium  phosphate.  It  is  soluble  in  alkalies  or  mineral 
acids,  but  not  in  acetic  acid.     If  a  solution  of  this  salt  in  acids  is 


neutralized  with  ammonia,  a  basic  phosphate  is  precipitated  hav- 
ing the  composition  3Al,(OH)3PO,-|-2Al(OH)3.  The  mineral 
Wavellite  has  this  composition,  with  nine  molecules  of  water. 
The  mineral  Kalait  contains  AlP04+Al(OH)3+H20,  and  when 
it  is  colored  azure  blue  by  a  little  copper  it  forms  the  Turquois. 
Aluminium  meta-phosphate  has  the  formula  AIP3O9  or  AI2O3.- 

Aluminium  Carbonate. 

If  to  a  cold  solution  of  alum  a  cold  solution  of  sodium  carbon- 
ate is  added  drop  by  drop,  stirring  constantly  until  the  solution 
reacts  feebly  alkaline,  a  precipitate  is  obtained  which,  after  be- 
ing washed  with  cold  water  containing  carbonic  acid  gas,  con- 
tains when  damp  single  equivalents  of  alumina  and  carbonic 
acid,  ALjOa.COij.  If  the  precautions  indicated  are  not  used,  the 
precipitate  contains  a  very  small  proportion  of  carbonic  acid. 

Sestini  *  states  that  one  litre  of  water  saturated  with  carbonic 
acid  gas  at  the  ordinary  atmospheric  pressure  will  dissolve  10 
milligrammes  of  alumina,  the  solution  becoming  turbid  on 
boiling  or  agitation.  This  reaction  is  probably  the  key  to  the 
understanding  of  the  geological  formation  of  native  alumina 

When  a  solution  of  sodium  bi-carbonate  is  added  to  one  of 
sodium  aluminate,  a  double  carbonate  of  the  alkali  and  alumin- 
ium is  precipitated,  which  is  easily  soluble  in  acids.  (Mende- 

Aluminium  Borate. 

Formula  3AI2OS.BO3.  Prepared  by  Ebelman  by  heating 
together  alumina,  oxide  of  cadmium,  and  boric  acid.  After 
three  days'  heating  the  platinum  capsule  containing  the  mix- 
ture was  found  covered  with  transparent  crystals  of  the  above 
composition,  hard  enough  to  scratch  quartz  and  having  a  spe- 
cific gravity  of  3.  Troost  obtained  the  same  substance  by 
heating  alumina  in  the  vapor  of  boron  trichloride.  Fremy  pre- 
pared  it  by  heating  fluoride  of   aluminium  with    boric  acid. 

*  Gazetta  Chim.,  Vol.  20,  p.  313. 


Ebelman  also  obtained  it  by  heating  a  mixture  of  alumina  and 
borax  to  whiteness ;  under  these  conditions  crystals  of  corun- 
dum were  formed  at  the  same  time. 

By  precipitating  a  cold  solution  of  alum  with  sodium  borate, 
double  salts  are  obtained  containing  soda,  but  which  leave  on 
washing  with  warm  water  two  compounds  having  the  formulae 
zAlA-BOs.sH.O  and  3Al203.2B03.8H,0.  If  the  washing  is 
prolonged  too  far  the  two  salts  are  completely  decomposed, 
leaving  a  residue  of  pure  alumina. 

Aluminium  Silicates. 

These  compounds  are  very  plentiful  in  nature,  both  hydrous 
and  anhydrous.  The  addition  of  a  soluble  aluminium  salt  to  a 
solution  of  sodium  silicate  would  doubtless  produce  a  precipi- 
tate of  aluminium  silicate.  Many  of 'the  native  silicates  have 
been  formed  by  the  mingling  of  lime  or  alkaline  water  with 
cabonated  water  carrying  alumina  in  solution.  In  the  native 
silicates  the  silica  and  alumina  occur  in  many  proportions ; 
the  following  ratios  of  alumina  to  silica  have  been  observed : 
2-1,  3-2,  i-i,  2-3,  1-2,  1-3,  1-4,  1-8,  thus  varying  from 
tri-basic  silicates  to  pent-acid  silicates.  The  pure  silicates 
of  aluminium  alone  are  infusible  before  the  blowpipe ;  but 
the  presence  of  other  elements,  especially  the  alkalies,  calcium 
or  iron,  makes  them  quite  easy  to  melt.  Ordinary  blast- 
furnace slags  are  silicates  of  aluminium,  calcium  and  magne- 
sium, and  vary  from  bi-acid  to  sesqui-basic  silicates.  In  some 
of  these  more  basic  silicates  part  of  the  aluminium  present  may 
exert  its  acid  character,  and,  in  fact,  the  occurrence  of  crystals 
of  magnesium  aluminate  has  been  noted  in  crystallized  blast- 
furnace slag  which  was  basic  and  rich  in  magnesium. 



We  will  consider  this  division  under  four  heads : — 

I.  Alumina. 
II.  Aluminium  chloride  and  aluminium-sodium  chloride. 

III.  Aluminium  fluoride  and  aluminium-sodium  fluoride. 

IV.  Aluminium  sulphide. 

The  Preparation  of  Alumina. 

We  will  treat  this  subject  in  three  divisions : — 

1 .  From  Aluminium  Sulphate  or  Alums. 

2.  From  Bauxite. 

3.  From  CryoHte. 

I.  Preparation  of  Alumina  from  Alums  or  Aluminium 


Hydrated  alumina  can  be  precipitated  from  a  solution  of  any 
aluminium  salt  by  ammonium  hydrate,  an  excess  of  which  re- 
dissolves  a  portion.  Its  chemical  formula  is  ordinarily  written 
AI2O3.3H2O  or  A^OHg).  The  aluminium  hydrate  thus  pre- 
cipitated is  a  pure  white,  very  voluminous,  almost  pasty  mass, 
very  hard  to  wash.  By  boiling  and  washing  with  boiUng  water 
it  becomes  more  dense,  but  always  remain  very  voluminous. 
Washing  on  a  filter  with  a  suction  apparatus  gives  the  best  re- 
sults. At  a  freezing  temperature  this  hydrate  changes  into  a 
dense  powder  which  is  more  easily  washed.  On  drying,  it 
shrinks  very  much  in  volume  and  forms  dense,  white  pieces, 
transparent  on  the  edges.  When  dried  at  ordinary  tempera- 
tures   it   has    the    composition    AljOg.H^O.     On    ignition,  the 



Other  molecule  of  water  is  driven  off,  leaving  anhydrous  alu- 
mina. After  gentle  ignition  it  remains  highly  hygroscopic,  and 
in  a  very  short  time  will  take  up  from  the  air  1 5  per  cent,  of 
water.  In  this  condition  it  is  easily  soluble  in  hydrochloric  or 
sulphuric  acid.  On  stronger  ignition  it  becomes  harder  and 
soluble  only  with  difficulty  in  concentrated  acid ;  after  ignition 
at  a  high  temperature  it  is  insoluble,  and  can  only  be  brought 
into  solution  again  by  powdering  finely  and  fusing  with  potas- 
sium acid-sulphate  or  alkaline  carbonate.  At  ordinary  furnace 
temperatures  alumina  does  not  melt,  but  in  the  oxy- hydrogen 
blow-pipe  or  the  electric  arc  it  fuses  to  a  limpid  Hquid  and  ap- 
pears crystalline  on  cooling. 

The  precipitation  in  aqueous  solution  and  subsequent  ignition 
is  not  economical  enough  to  be  practised  on  a  large  scale,  and 
for  industrial  purposes  the  aluminium  sulphate  or  alum  is  ig- 
nited directly.  About  the  easiest  way  to  proceed  is  to  take 
ammonia  alum  crystals,  put  them  into  a  clean  iron  pan  and 
heat  gently,  when  the  salt  melts  in  its  water  of  crystallization. 
When  the  water  has  evaporated,  a  brittle,  shining,  sticky  mass 
remains,  which  on  further  heating  swells  up  and  decomposes 
into  a  dry,  white  powder.  This  is  let  cool,  powdered,  put  into 
a  crucible  and  heated  to  bright  redness.  All  the  ammonia  and 
almost  all  the  sulphuric  acid  are  thus  removed.  The  rest  of 
the  acid  can  be  removed  by  moistening  the  mass  with  a  solu- 
tion  of  sodium  carbonate,  drying  and  again  igniting ;  on  wash- 
ing with  water  the  acid  is  removed  as  sodium  sulphate.  The 
residue,  however,  will  contain  some  caustic  soda,  which  for  its 
further  use  in  making  aluminium  chloride  is  not  harmful.  Pot- 
ash alum  can  be  treated  in  a  similar  way,  the  potassium  sul- 
phate being  washed  away  after  the  first  ignition.  Still  more 
easily  and  cheaply  can  alumina  be  made  by  igniting  a  mixture 
of  4  parts  aluminium  sulphate  and  i  of  sodium  carbonate.  On 
washing,  sodium  sulphate  is  removed  from  the  alumina.* 

Deville  used  the  following  method  at  Javel :  Ammonia  alum  or 

*  Kerl  and  Stohman,  4th  Ed.,  p.  739. 


even  the  impure  commercial  aluminium  sulphate  was  calcined, 
the  residue  appearing  to  be  pure,  white  alumina,  but  it  still  con- 
tained sulphuric  acid,  potassium  sulphate,  and  a  notable  pro- 
portion of  iron.  This  alumina  is  very  friable,  and  is  passed 
through  a  fine  sieve,  and  put  into  an  iron  pot  with  twice  its 
weight  of  solution  of  caustic  soda  of  45  degrees.  It  is  then 
boiled  and  evaporated,  and  the  alumina  dissolves  even  though 
it  has  been  strongly  calcined.  The  aluminate  of  soda  produced 
is  taken  up  in  a  large  quantity  of  water,  and  if  it  does  not  show 
clear  immediately,  a  little  sulphuretted  hydrogen  is  passed  in, 
which  hastens  the  precipitation  of  the  iron.  The  liquor  is  let 
stand,  the  clear  solution  decanted  ofT  and  subjected  while  still 
warm  to  the  action  of  a  stream  of  carbonic  acid  gas.  This  con- 
verts the  soda  into  carbonate  and  precipitates  the  alumina  in  a 
particularly  dense  form  which  collects  in  a  space  not  one- 
twentieth  of  the  volume  which  would  be  taken  up  by  gelatinous 
alumina.  This  precipitate  is  best  washed  by  decantation,  but  a 
large  number  of  washings  are  necessary  to  remove  all  the  sodium 
carbonate  from  it ;  it  is  even  well,  before  finishing  the  washing, 
to  add  a  little  sal-ammoniac  to  the  wash-water  in  order  to  hasten 
the  removal  of  the  soda.  The  well-dried  alumina  is  calcined  at 
a  red  heat. 

Tilghman*  decomposes  commercial  sulphate  of  alumina, 
Al2(S04)3.i8H20,  by  filling  a  red-hot  fire-clay  cylinder  with  it. 
This  cylinder  is  lined  inside  with  a  magnesia  fettUng,  is  kept  at 
a  red  heat,  the  sulphate  put  in  in  large  lumps,  and  steam  is 
passed  through  the  retort,  carrying  with  it  vapor  of  sodium 
chloride.  This  last  arrangement  is  effected  by  passing  steam 
into  a  cast-iron  retort  in  which  the  salt  named  is  kept  melted, 
and  as  the  steam  leaves  this  retort  it  carries  vapor  of  the  salt 
with  it.  It  is  preferable,  however,  to  make  a  paste  of  the  sul- 
phate of  alumina  and  the  sodium  chloride,  forming  it  into  small 
hollow  cylinders,  which  are  well  dried,  and  then  the  fire-clay 
cylinder  filled  with  these.     Then,  the  cylinder  being  heated  to 

*  Mierzinski. 


whiteness,  highly  superheated  steam  is  passed  over  it.  The 
hydrochloric  acid  gas  which  is  formed  is  caught  in  a  condensing 
apparatus,  and  there  remains  a  mass  of  aluminate  of  soda, 
which  is  moistened  with  water  and  treated  with  a  current  of 
carbon  dioxide  and  steam.  By  washing  the  mass,  the  soda 
goes  fnto  solution  and  hydrated  alumina  remains,  which  is 
washed  well  and  is  ready  for  use. 

Mr.  Webster's  process  for  making  pure  alumina  at  a  low  price 
was  incorporated  as  a  part  of  the  Aluminium  Co.  Ld.'s  pro- 
cesses.    The  only  description  we  can  give  of  it  is  dated  1883. 

*  Three  parts  of  potash  alum  are  mixed  with  one  part  of 
pitch,  placed  in  a  calcining  furnace  and  heated  to  200°  or  250°. 
About  40  per  cent,  of  this  water  is  thus  driven  off,  leaving  sul- 
phate of  potash  and  aluminium,  with  some  ferric  oxide.  After 
heating  about  three  hours,  the  pasty  mass  is  taken  out,  spread 
on  a  stone  floor,  and  when  cold  broken  to  pieces.  Hydrochloric 
acid  (20  to  25  per  cent.)  is  poured  upon  these  pieces,  placed 
in  piles,  which  are  turned  over  from  time  to  time.  When  the 
evolution  of  sulphuretted  hydrogen  has  stopped,  about  five  per 
cent,  of  charcoal-powder  or  lampblack,  with  enough  water  to 
make  a  thick  paste,  is  added.  The  mass  is  thoroughly  broken 
up  and  mixed  in  a  mill,  and  then  worked  into  balls  of  about  a 
pound  each.  These  are  bored  through  to  facilitate  drying,  and 
heated  in  a  drying  chamber  at  first  to  40°,  then  in  a  furnace 
from  95°  to  150°.  The  balls  are  then  kept  for  three  hours  at' 
a  low  red  heat  in  retorts,  while  a  mixture  of  two  parts  steam 
and  one  part  air  is  passed  through,  so  that  the  sulphur  and  car- 
bon are  converted  into  sulphurous  oxide  and  carbonic  oxide, 
and  thus  escape.  The  current  of  gas  carries  over  some  potas- 
sium sulphate,  ferrous  sulphate  and  alumina,  and  is  therefore 
passed  through  clay  condensers. 

The  residue  in  the  retorts  consists  of  alumina  and  potassium 
sulphate ;   it   is   removed,  ground    to    fine    powder    in    a  mill, 

♦Austrian  Patent,  Sept.  28,  1882;  English  patent.  No.  2580,  1881.  Dingier,  1883, 
vol.  259,  p.  86. 


treated  with  about  seven  times  its  weight  of  water,  boiled  in  a 
pan  or  boiler  by  means  of  steam  for  about  one  hour,  then 
allowed  to  stand  till  cool.  The  solution  containing  the  potas- 
sium sulphate  is  run  ofifand  evaporated  to  dryness,  the  alumina 
is  washed  and  dried.  The  potassium  sulphate,  as  a  by-product, 
is  said  to  pay  one-half  the  cost  of  the  process. 

This  deposit  contains  about  84  per  cent,  of  alumina,  while 
that  obtained  by  the  old  process  of  precipitation  has  only  65 
per  cent.  Thus  a  large  saving  is  effected  in  cost,  and  19  per 
cent,  more  alumina  is  obtained.  In  addition  to  this,  the  whole 
of  the  by-products  are  recovered,  consisting  of  potassium  sul- 
phate, sulphur  (which  is  used  in  making  sulphuric  acid),  and 
aluminate  of  iron. 

2.  Preparation  of  Alumina  from  Bauxite. 

At  Salindres,  the  alumina  used  in  the  Deville  process  was 
obtained  from  bauxite  by  the  following  processes,  which  are 
in  general  use  for  extracting  pure  alumina  from  this  mineral. 
Bauxite  is  plentiful  enough  in  the  south  of  France,  principally 
in  the  departments  of  Herault,  Bouches-du-Rhone,  and  Var. 
It  contains  as  much  as  seventy-five  per  cent,  alumina.  To 
separate  the  alumina  from  ferric  oxide,  it  is  treated  with  car- 
bonate of  soda,  under  the  influence  of  a  sufiSciently  high  tem- 
perature, the  alumina  displacing  the  carbonic  acid  and  forming 
an  aluminate  of  soda,  Al^Og.sNa^O,  while  the  ferric  oxide  re- 
mains unattacked.  A  simple  washing  with  water  then  permits 
the  separation  of  the  former  from  the  insoluble  ferric  oxide. 
The  bauxite  is  first  finely  pulverized  by  means  of  a  vertical 
mill-stone,  then  intimately  mixed  with  some  sodium  carbonate. 
The  mixture  is  made,  for  one  operation,  of — 

480  kilos,  bauxite. 

300      "     sodium  carbonate  of  90  alkali  degrees. 

This  mixture  is  introduced  into  a  reverberatory  furnace,  re- 
sembling in  form  a  soda  furnace,  and  which  will  bear  heating 


Strongly.  The  mass  is  stirred  from  time  to  time,  and  it  is  kept 
heated  until  all  the  carbonate  has  been  attacked,  which  is 
recognized  by  a  test  being  taken  which  does  not  effervesce 
with  acids.     The  operation  lasts  from  five  to  six  hours. 

The  aluminate  thus  obtained  is  separated  from  ferric  oxide  by 
a  washing  with  warm  water.  This  washing  is  made  at  first  with 
a  feeble  solution  which  has  served  for  the  complete  exhaustion 
of  the  preceding  charge,  which  was  last  washed  with  pure 
water,  forming  thus  this  feeble  solution.  This  gives,  on  the 
first  leaching,  solutions  of  aluminate  concentrated  enough  to  be 
called  strong  liquor,  which  are  next  treated  by  the  current  of 
carbonic  acid  gas  to  precipitate  the  hydrated  alumina.  The 
charge  is  next  washed  with  pure  water,  which  completely  re- 
moves the  aluminate ;  this  solution  is  the  weak  liquor,  which  is 
put  aside  in  a  special  tank,  and  used  as  the  first  leaching  liquor 
on  the  next  charge  treated.  This  treatment  takes  place  in  the 
following  apparatus  (see  Fig.  i ) :  ^  is  a  sheet-iron  vessel,  in 
the  middle  of  which  is  a  metallic  grating,  F,  on  which  is  held 
all  round  its  edges,  by  pins,  a  cloth,  serving  as  a  filter.  A 
ought  to  be  closed  by  a  metallic  lid  held  on  firmly  by  bolts. 
To  work  the  apparatus,  about  500  kilos  of  the  charge  to  be 
washed  is  placed  on  the  filter  cloth,  the  lid  is  closed,  then 
the  steam-cock  /  of  the  reservoir  A  is  opened.  In  A  is  the 
weak  solution  from  the  last  washing  of  the  preceding  charge. 
The  pressure  of  the  steam  makes  it  rise  by  the  tube  T  into  the 
filter;  another  jet  of  steam,  admitted  by  the  cock  b,  rapidly 
warms  the  feeble  liquor  as  it  soaks  into  the  charge.  After  fil- 
tering through,  the  strong  liquor  is  drawn  off  by  turning  the 
stop-cock  G.  The  weak  solution  of  the  reservoir  A  is  put  into 
the  filter  in  successive  portions,  and  not  all  at  once ;  and  after 
each  addition  of  solution  has  filtered  through,  its  strength  in 
B.°  is  taken,  before  any  more  solution  is  run  in ;  then,  when  the 
solution  marks  3°  to  4°,  it  is  placed  in  a  special  tank  for  weak 
liquor,  with  all  that  comes  through  afterwards.  Just  about  this 
time,  the  weak  liquor  of  the  reservoir  A  is  generally  all  used  up, 
and  is  replaced  by  pure  water  introduced  by  the  tube  d.     All 



the  solutions  which  filtered  through  marking  over  3°  to  4°  B., 
are  put  together,  and  form  a  strong  liquor  which  marks  about 
12°  B.  This  extraction  of  the  aluminate  being  completed  by 
the  pure  water,  the  residue  on  the  filter  is  taken  out,  and  a  new 
operation  may  be  commenced. 

Fig.  I. 




Li— p 












i-cvrrrpe  O 

The  strong  liquor  is  introduced  into  a  vessel  having  an  agi- 
tator, where  a  strong  current  of  carbonic  acid  gas  may  precipi- 
tate the  alumina  from  it.  The  gas  is  produced  by  small  streams 
of  hydrochloric  acid  continuously  falling  on  some  limestone 
contained  in  a  series  of  earthenware  jars.  The  precipitation 
vessel  is  called  a  baratte.  The  carbonic  acid  after  having 
passed  through  a  washing-flask,  is  directed  to  a  battery  of  three 
barattes,  where  the  precipitation  is  worked  methodically,  so  as 
to  precipitate  completely  the  alumina  of  each  baratte,  and  util- 



ize  at  the  same  time  all  the  carbon  dioxide  produced.  In  order 
to  do  this,  the  gas  always  enters  first  into  a  baratte  in  which 
the  precipitation  is  nearest  completion,  and  arrives  at  last  to 
that  in  which  the  solution  is  freshest.  When  the  gas  is  not  all 
absorbed  in  the  last  baratte,  the  first  is  emptied,  for  the  precip- 
itation in  it  is  then  completed,  and  it  is  made  the  last  of  the 
series,  the  current  being  now  directed  first  into  the  baratte 
which  was  previously  second,  while  the  newly  charged  one  is 
made  the  last  of  the  series.  The  process  is  thus  kept  on  con- 
tinuously.    The  apparatus  used  is  shown  in  Fig.  2, 

Fig.  2. 

u.  Charging  pipe.  b.  Steam  pipe.  i.  Steam  drip.  d.  COj  enters.  /  Discharge 
pipe.  A.  Agitator,  made  of  iron  rods.  C.  Tank  in  which  the  precipitate  settles. 
B.  Baratte  body.    D.  Steam  jacket. 

Each  baratte  holds  about  1200  litres  of  solution,  and  the 
complete  precipitation  of  all  the  alumina  in  it  takes  five  to  six 
hours.  A  mechanical  agitator  stirs  the  contents  continually, 
and  a  current  of  steam  is  let  into  the  double  bottom  so  as  to 


keep  the  temperature  of  the  solution  about  70°.  The  precipi- 
tated alumina  and  the  solution  of  sodium  carbonate  which  re- 
main are  received  in  a  vat  placed  beneath  each  baratte.  The 
solution  is  decanted  off  clear,  after  standing,  and  then  evapor- 
ated down  to  dryness,  regenerating  the  sodium  carbonate  used 
in  treating  the  bauxite  to  make  the  aluminate,  less  the  inevit- 
able losses  inseparable  from  all  industrial  operations.  The  de- 
posit of  alumina  contains  considerable  sodium  carbonate  me- 
chanically intermixed,  and  is  put  into  a  conical  strainer  to 
drain,  or  else  into  a  centrifugal  drying  machine,  which  rapidly 
drives  out  of  the  hydrated  alumina  most  of  the  solution  of 
sodium  carbonate  which  impregnates  it ;  a  washing  with  pure 
water  in  the  drier  itself  terminates  the  preparation  of  the 
alumina.  At  the  works  at  Salindres,  a  part  of  this  alumina  is 
converted  into  sulphate  of  alumina,  which  is  sold,  the  remainder 
being  used  for  the  aluminium  manufacture.  After  washing  in 
the  drier,  the  alumina  presents  this  composition : — 

Alumina 47.5 

Water 50.0 

Sodium  carbonate 2.5 

Behnke*  produces  alumina  by  igniting  bauxite  or  a  similar 
mineral  with  sodium  sulphate,  carbon,  and  ferric  oxide,  using 
for  each  equivalent  of  alumina  present  at  least  one  equivalent 
of  alkali  and  one-half  an  equivalent  of  ferric  oxide.  The  mix- 
ture is  heated  in  a  muffle  or  reverberatory  furnace.  The  fritted 
product  is  ground,  exposed  to  the  air,  and  washed  with  water. 
Sodium  aluminate  goes  into  solution  along  with  some  sodium 
sulphate,  while  ferrous  sulphide  and  undecomposed  material 
remains  as  a  residue.  By  passing  carbonic  acid  gas  or  gases 
from  combustion  through  the  solution,  the  alumina  is  precip- 
itated. The  residue  spoken  of  is  roasted,  the  sulphurous  oxide 
given  off  utilized,  and  the  residue  used  over  in  place  of  fresh 
ferric  oxide. 

R.  Lieber  f  proposes  to  treat  bauxite,  aluminous  iron  ore, 

*  German  Patent  (D.  R.  P.),  No.  7256. 
t  German  Patent  (D.  R.  P.),  No.  5670. 


etc.,  in  a  somewhat  similar  way.  These  materials  are  to  be 
ground  fine,  mixed  with  sodium  chloride  and  magnesium  sul- 
phate (Kieserite),  moistened  with  water,  and  pressed  into 
bricks  or  balls.  These  are  dried  and  put  into  a  retort  heated 
red-hot  by  generator  gas.  Hydrochloric  acid  gas  is  first  given 
off,  sodium  sulphate  and  magnesium  chloride  being  formed. 
In  a  further  stage  of  the  process  sulphurous  oxide  is  evolved, 
the  alumina  reacting  on  the  sodium  sulphate  to  form  sodium 
aluminate.  The  latter  is  washed  out  of  the  residue,  and  its 
alumina  precipitated  by  the  ordinary  methods. 

H.  Muller*  proposes  to  extract  the  alumina  from  silicates 
containing  it  by  mixing  them  with  limestone,  dolomite,  or 
magnesite,  also  with  alkali  caustic,  carbonate,  or  sulphate  (in 
the  last  case  also  with  carbon),  and  heating  the  mixture  to 
bright-redness.  Alkaline  aluminate  is  washed  out  of  the  re- 
sulting mass,  while  the  residue,  consisting  of  lime,  magnesia, 
iron  oxide,  etc.,  is  mixed  wifh  water-glass  and  moulded  into 
artificial  stone. 

Common  salt  is  said  not  to  react  on  bauxite  if  fused  with  it 
alone,  but  will  decompose  it  if  steam  is  used.  Tilghmanf  first 
used  this  reaction  in  1847.  It  is  said  that  it  was  also  used  at 
Nanterre  and  Salindres  previously  to  1865.  A  mixture  of 
sodium  chloride  and  bauxite  was  treated  in  a  closed  retort  and 
steam  passed  through,  or,  better,  in  a  reverberatory  furnace  an(J 
steam  passed  over  it,  at  a  high  temperature.  Much  sodium 
chloride  must  have  been  lost  by  the  latter  arrangement.  The 
fused  mass  was  treated  with  water,  when  sodium  aluminate  dis- 
solved out. 

R.  WagnerJ  proposed  to  make  a  solution  of  sodium  sulphide, 
by  reducing  sodium  sulphate  by  carbon  bisulphide,  and  to  boil 
the  bauxite  in  it.  The  sulphuretted  hydrogen  evolved  was  to 
be   absorbed  by  ferric  hydrate;  while  the  sodium  aluminate 

*  German  Patent  (D.  R.  P.),  No.  12,947. 
t  Polytechnisches  Journal,  106,  p.  196. 
J  Wagner's  Jahresb.,  1865,  p.  332. 


was  converted  into  soda  and  alumina  by  any  of  the  ordinary 

Laur,  a  manufacturer  of  alumina  in  the  south  of  France,  has 
attempted  to  use  sodium  sulphate  instead  of  the  carbonate,  in 
calcining  bauxite.  He  finds  it  disadvantageous  to  exclude  the 
carbonate  altogether,  but  uses  for  a  bauxite  containing  20  per 
cent,  of  ferric  oxide  and  60  per  cent,  of  alumina,  about  66  of 
sodium  sulphate  and  16  of  sodium  carbonate  per  100  of  baux- 
ite. Carbon  must  also  be  mixed  with  the  charge.  Under 
these  conditions  the  ferric  oxide  present  is  first  reduced  to  iron, 
which  finally  becomes  iron  sulphide.  The  soda  from  both  the 
carbonate  and  the  sulphate  combines  with  the  alumina  to  form 
aluminate.  An  excess  of  soda  is  necessary  to  keep  -the 
aluminate  in  solution,  and  to  keep  the  sulphide  of  iron  out  of 
solution.  The  rest  of  the  process  is  similar  to  that  already  de- 
scribdti  at  Salindres. 

According  to  Lowig's  experiments,  solution  of  sodium  alumi- 
nate can  be  precipitated  by  calcium,  barium,  strontium,  or 
magnesium  hydrates,  forming  caustic  soda  and  hydrated 
alumina,  the  latter  being  precipitated,  together  with  lime, 
baryta,  strontia,  or  magnesia.  The  precipitate  is  washed  by 
decantation,  and  then  divided  into  two  portions,  one  of  which 
is  dissolved  in  hydrochloric  acid,  the  other  made  into  a  mush 
with  water,  and  gradually  added  to  the  solution  of  the  first  half 
until  the  filtrate  shows  only  a  very  little  alumina  in  solution. 
Chloride  of  calcium,  barium,  strontium,  or  magnesium  has  been 
formed,  and  the  alumina  all  precipitated. 

Dr.  K.  J.  Bayer  has  made  an  improvement  in  the  process  of 
extracting  alumina  from  bauxite,  which  has  received  great 
commendation  from  those  directly  interested  in  the  business, 
and  who  may  be  supposed  to  have  proved  its  merits.  Dr. 
Bayer  thus  describes  it :  *  Bauxite  is  fused  with  sodium  car- 
bonate or  sulphate,  and  the  solution  obtained  by  washing, 
containing  sodium  aluminate,  is  not  decomposed  by  carbonic 

*  Stahl  und  Eisen,  Feb.  1889,  p.  112. 


acid,  as  formerly,  but  by  the  addition  of  aluminium  hydrate 
with  constant  stirring.  The  decomposition  of  the  solution  goes 
on  until  the  quantity  of  alumina  remaining  in  solution  is  to  the 
sodium  protoxide  as  i  to  6.  This  preciptation  takes  place  in 
the  cold,  and  the  pulverulent  aluminium  hydrate  separted  out 
is  easily  soluble  in  acids.  The  alkaline  solution  remaining  is 
concentrated  by  evaporation,  taken  up  by  ground  bauxite, 
dried,  calcined,  and  melted,  and  thus  goes  through  the  process 
again.  The  use  of  this  caustic  soda  solution  containing  alumina 
is  thus  much  more  profitable  than  using  soda,  because  by  using 
the  latter  only  75  per  cent,  of  the  bauxite  used  is  utilized, 
whereas  by  the  former  all  th«  alumina  dissolved  by  the  solution 
is  obtained  again. 

3.  Preparation  of  Alumina  from  Cryolite. 

By  the  Dry  Way. — The  following  method  was  invented  by 
Julius  Thomson ;  the  description  is  taken  principally  from  Mier- 
zinski's  "  Fabrikation  des  Aluminiums  :"  The  cryolite  is  pulver- 
ized, an  easy  operation,  and  to  every  lOO  parts,  130  to  150 
parts  of  chalk  are  added,  and  a  suitable  quantity  of  fluorspar 
is  also  used,  which  remains  in  the  residue  on  washing  after  ig- 
nition. More  chalk  is  used  than  is  theoretically  necessary,  in 
order  to  make  the  mass  less  fusible  and  keep  it  porous.  But, 
to  avoid  using  too  much  chalk  merely  for  this  purpose,  a  cer- 
tain quantity  of  coke  may  be  put  into  the  mixture.  It  is  of  the" 
first  importance  that  the  mixture  be  very  intimate  and  finely 
pulverized.  It  is  of  greater  importance  that  the  mixture  be 
subjected  to  just  the  proper  well-regulated  temperature  while 
being  calcined.  The  cryolite  will  melt  very  easily,  but  this  is 
to  be  avoided.  On  this  account,  the  calcination  cannot  take 
place  in  an  ordinary  smelting  furnace,  because,  in  spite  of  stir- 
ring, the  mass  will  melt  at  one  place  or  another,  while  at  an- 
other part  of  the  hearth  it  is  not  even  decomposed,  because 
the  heat  at  the  fire-bridge  is  so  much  higher  than  at  the  farther 
end  of  the  hearth.  Thomson  constructed  a  furnace  for  this 
special  purpose   (see  Figs.  3  and  4),  in  which  the  flame  from 


1 45 

the  fire  first  went  under  the  bed  of  the  furnace,  then  over  the 
charge  spread  out  on  the  bed,  and  finally  into  a  flue  over  the 
roof  of  the  hearth.  The  hearth  has  an  area  of  nearly  9  square 
metres,  being  4  metres  long  and  2.5  metres  wide.    It  is  charged 

Fig.  3. 


twelve  times  each  day,  each  time  with  500  kilos  of  mixture, 
thus  roasting  6000  kilos  daily,  with  a  consumption  of  800  kilos 
of  coal.    The  waste  heat  of  the  gases  escaping  from  the  furnace 

Fig.  4. 


is  utilized  for  drying  the  soda  solution  to  its  crystallizing  point, 
and  the  gases  finally  pass  under  an  iron  plate  on  which  the 
chalk  is  dried.  In  this  furnace  the  mass  is  ignited  thoroughly 
without  a  bit  of  it  melting,  so  that  the  residue  can  be  fully 
washed  with  water. 


The  decomposition  takes  place  according  to  the  formula — 

2  (AlFs-sNaF)  +  6CaC03=Al203.3Na20  +  6CaF,  +  6C0„ 

the  resultant  product  containing  aluminate  of  soda,  soluble  in 
water,  and  insoluble  calcium  flouride.  The  reaction  com- 
mences at  a  gentle  heat,  but  is  not  completed  until  a  red  heat 
is  reached.  Here  is  the  critical  point  of  the  whole  process, 
since  a  very  little  raising  of  the  temperature  above  a  red  heat 
causes  it  to  melt.  However,  it  must  not  be  understood  that  the 
forming  of  lumps  is  altogether  to  be  avoided.  These  lumps 
would  be  very  hard  and  unworkable  when  cold,  but  they  can  be 
broken  up  easily  while  hot,  so  that  they  may  be  drawn  out  of 
the  furnace  a  few  minutes  before  the  rest  of  the  charge  is  re- 
moved, and  broken  up  while  still  hot  without  any  trouble. 
The  whole  charge,  on  being  taken  out,  is  cooled  and  sieved,  the 
hard  lumps  which  will  not  pass  the  sieve  are  ground  in  a  mill 
and  again  feebly  ignited,  when  they  will  become  porous  and 
may  be  easily  ground  up.  However,  the  formation  of  these 
lumps  can  be  avoided  by  industrious  stirring  of  the  charge  in 
the  furnace.  A  well-calcined  mixture  is  porous,  without  dust 
and  without  lumps  which  are  too  hard  to  be  crushed  between 
the  fingers.  We  would  here  remark  that  mechanical  furnaces 
of  similar  construction  to  those  used  in  the  manufacture  of  soda, 
potash,  sulphate  of  soda,  etc.,  are  more  reliable  and  give  the 
best  results  if  used  for  this  calcination.  The  mixture,  or  ashes, 
as  the  workmen  call  it,  is  drawn  still  hot,  and  washed  while 
warm  in  conical  wooden  boxes  with  double  bottoms,  or  the  box 
may  have  but  one  bottom,  with  an  iron  plate  about  "]&  milli- 
metres above  it.  A  series  of  such  boxes,  or  a  large  apparatus 
having  several  compartments,  may  be  so  arranged  that  the 
washing  is  done  methodically,  i.  e.,  the  fresh  water  comes  first 
in  contact  with  a  residue  which  is  already  washed  nearly  clean, 
and  the  fresh  charge  is  washed  by  the  strong  liquor.  This  is 
known  as  the  "  Lessiveur  methodique,"  and  an  apparatus  con- 
structed especially  for  this  purpose  is  described  in  Dingier  186, 
376,  by  P.  J.  Havrez,  but  the  subject  is  too  general  and  the  de- 


scription  too  long  to  be  given  here.  A  very  suitable  washing 
apparatus  is  also  the  Buff-Dunlop,  used  in  the  soda  industry 
for  washing  crude  soda,  and  described  in  Lunge's  "  Sulphuric 
Acid  and  Alkali,"  Book  II.,  p.  465.  Since  the  ashes  are 
taken  warm  from  the  furnace  the  washing  water  need  not  be 
previously  heated,  but  the  final  wash-water  must  be  warmed,  as 
the  ashes  have  been  cooled  down  by  the  previous  washings. 
As  soon  as  the  strong  liquor  does  not  possess  a  certain 
strength,  say  20°  B.,  it  is  run  over  a  fresh  charge  and  so 
brought  up.     The  solution  contains  sodium  aluminate. 

The  carbon  dioxide  necessary  for  precipitating  the  hydrated 
alumina  may  be  made  in  different  ways.  The  gases  coming 
from  the  furnace  in  calcining  the  cryolite  might  be  used  if  they 
were  not  contaminated  with  dust;  and  there  is  also  the  diffi- 
culty that  exhausting  the  gases  from  the  furnace  would  inter- 
fere with  the  calcination.  It  has  also  been  recommended  to 
use  the  gases  from  the  fires  under  the  evaporating  pans,  by 
exhausting  the  air  from  the  flues  and  purifying  it  by  washing 
with  water.  This  can  only  be  done  where  the  pans  are  fired 
with  wood  or  gas.  However,  the  lime-kiln  is  almost  exclu- 
sively used  to  furnish  this  gas.  The  kiln  used  is  shaped  like  a 
small  blast  furnace.  Leading  in  at  the  boshes  are  two  flues 
from  five  fire-places  built  in  the  brickwork  of  the  furnace,  and 
the  heat  from  these  calcines  the  limestone.  The  gases  are 
taken  ofT  by  a  cast-iron  down-take  at  the  top.  At  the  bottom 
of  the  furnace,  corresponding  with  the  tap  hole  in  a  blast  fur- 
nace, is  an  opening,  kept  closed,  from  which  lime  is  withdrawn 
at  intervals.  A  strong  blast  is  blown  just  above  the  entrance 
of  the  side  flues,  and  by  keeping  up  a  pressure  in  the  furnace, 
leakings  into  it  may  be  avoided.  The  gas  is  sucked  away  from 
the  top  by  a  pump,  which  forces  it  through  a  cleaning  appar- 
atus constructed  like  a  wash-bottle,  and  it  is  then  stored  in  a 
gasometer.  Instead  of  the  pump,  a  steam  aspirator  may  be 
used,  which  is  always  cheaper  and  takes  up  less  room. 

The  precipitation  with  carbonic  acid  gas  is  made  by  simply 
forcing  it  through  a  tube  into  the  liquid.     The  apparatus  used 


at  Salindres  is  one  of  the  most  improved  forms.  (See  p.  140.) 
The  precipitate  is  granular,  and  settles  easily.  However,  it  is 
not  pure  hydrated  alumina,  but  a  compound  of  alumina,  soda, 
carbonic  acid,  and  water,  containing  usually  about — 

Alumina ■ 45  per  cent. 

Sodium  carbonate 20       " 

Water 35        " 

The  sodium  carbonate  must  be  separated  by  long-continued 
boiling  with  water,  but  by  this  treatment  the  alumina  becomes 
gelatinous  and  diflficult  of  further  treatment.  The  precipitate 
was  formerly  separated  on  linen  filters,  but  centrifugal  ma- 
chines are  now  preferred.  The  evaporated  solution  gives  a 
high  grade  of  carbonate  of  soda  free  from  iron.  The  heavy 
residue  which  is  left  after  the  ashes  have  been  lixiviated  con- 
sists of  calcium  fluoride  with  small  quantities  of  ferric  oxide, 
lime,  undecomposed  cryolite,  and  aluminate  of  soda,  and  has 
not  been  utilized  for  any  purpose. 

R.  Biederman*  states  that  if  steam  is  passed  over  molten 
cryolite  at  a  white  heat,  hydrofluoric  acid  gas  and  sodium 
fluoride  are  formed  and  driven  over,  while  a  white,  pure  crys- 
talline mass  of  alumina  remains. 

Utilization  of  aluminous  fluoride  slags. — At  Nanterre,  De- 
ville  used  the  following  process  for  utilizing  in  one  operation 
the  slags  from  the  aluminium  manufacture  and  the  residues 
from  the  sodium  manufacture. 

"  The  slags  from  making  aluminium  contain  60  per  cent,  of 
sodium  chloride  and  40  per  cent,  of  insoluble  matter;  the 
former  can  be  removed  by  a  single  washing.  The  insoluble 
material  is  almost  entirely  aluminium  fluoride,  with  a  little 
alumina  and  undecomposed  cryolite.  When  fluorspar  is  used 
as  a  flux,  the  sodium  chloride  in  the  slag  is  in  part  replaced  by 
calcium  chloride ;  but,  in  general,  all  the  fluorine  in  the  slag  is 
found  combined  with  the  aluminium,  which  shows  the  great 
affinity  between  these  two  elements.     The  residues  left  in  the 

*  Karl  and  Stohman,  4th  Ed.,  p.  819. 


sodium  retorts  deteriorate  quickly  when  exposed  to  the  air,  and 
contain  ordinarily,  according  to  my  analysis-^ 

Carbon 20.0 

Carbonate  of  soda 14.5 

Caustic  soda 8,3 

Sulphate  of  soda 2.4 

Carbonates  of  lime  and  iron 29.8 

Water 25.0 


"  To  utilize  these  two  materials,  5  to  6  parts  of  the  sodium 
residues  are  mixed  carefully  with  one  part  of  the  washed  slag, 
and  the  whole  calcined  at  a  red  heat.  The  fusion  becomes 
pasty ;  it  is  cooled  and  washed,  when  aluminate  of  soda  goes 
into  solution,  and  on  treatment  with  carbon  dioxide  gives 
sodium  carbonate  and  alumina.  According  to  my  laboratory 
experiments — 

1000  grammes  of  sodium  residues 
160        "         "  washed  slags 

have  given 

no  grammes  of  calcined  alumina 
225         "  "  dry  sodium  carbonate. 

"  The  residue  left  on  washing  the  fusion  weighs  about  one- 
half  the  weight  of  the  soda  residues  used,  and  contains — 

Carbon 30.0 

Calcium  fluoride 32.0 

Alumina 0.6 

Various  other  materials 37.4 

"  The  latter  item  is  formed  of  ferric  oxide,  oxide  of  man- 
ganese, a  little  silica  and  some  oxysulphide  of  calcium." 

Decomposition  of  Cryolite  in  the  Wet  Way. — Deville  used  the 
following  method  at  Javel,  which  he  thus  describes; — 

"  In  the  Greenland  cryolite  there  are  to  be  found  numerous 
pieces  containing  siderite  (ferrous  carbonate).     It  is  necessary 


to  extract  all  these  pieces  before  using  the  mineral  as  a  flux  in 
producing  aluminium.  The  rejected  fragments  are  then  util- 
ized by  pulverizing  them  finely,  mixing  with  about  three-fourths 
of  their  weight  of  pure,  burnt  lime  and  the  whole  carefully 
slaked.  After  the  slaking,  water  is  added  in  large  quantity, 
and  the  material  is  heated  in  a  large  cast-iron  vessel  by  means 
of  a  steam-coil.  A  reaction  takes  place  at  once,  and  is  com- 
plete if  the  process  is  well  conducted.  Some  insoluble  alum- 
inate  of  lime  may  be  formed,  but  it  can  be  recovered  from  the 
residue  by  digesting  itwith  some  solution  of  carbonate  of  soda. 
The  residue  remaining  is  calcium  fluoride,  which  settles  easily, 
and  the  clear  liquor  decanted  off  contains  aluminate  of  soda, 
from  which  alumina  can  be  precipitated  as  before.  The  cal- 
cined alumina  obtained  may  contain  iron  when  the  cryolite 
used  contains  a  large  amount  of  ferrous  carbonate.  It  has  ap- 
peared to  me  that  the  latter  mineral  may  be  decomposed  by 
the  lime,  and  some  protoxide  of  iron  be  thus  dissolved  by  the 
soda  in  small  quantity." 

"We  make  alumina  by  this  method  at  Nanterre  only  because 
it  utilizes  the  impure  pieces  of  cryolite  and  works  in  conveni- 
ently with  the  previously-described  processes  for  utilizing  the 

An  ingenious  modification  of  the  above  process  was  devised 
by  Sauerwein.  The  first  reaction  is  the  same,  five  parts  of 
finely-powdered  cryolite  being  boiled  with  four  parts  of  burnt 
lime,  as  free  as  possible  from  iron,  producing  a  solution  of 
sodium  aluminate  and  a  residue  of  insoluble  calcium  fluoride. 
Tissier  recommended  using  two  parts'  of  cryolite  to  one  of  lime, 
but  with  these  proportions  only  about  one-third  of  the  alumin- 
ium in  the  cryolite  is  converted  into  soluble  aluminate.  Hahn 
claims  that  complete  decomposition  takes  place  by  using  xoo 
parts  of  cryolite  to  88  parts  of  burnt  lime.  The  solution  is  set- 
tled, washed  by  decantation,  and  these  washings  put  with  the 
strong  solution  first  poured  off;  the  next  washings  are  reserved 
for  the  fresh  wash-water  of  another  operation.  The  solution  of 
sodium   aluminate  is   then   boiled  with  a  quantity  of   cryolite 


equal  to  the  amount  first  used,  when  sodium  fluoride  is  formed 
and  alumina  precipitated.  This  operation  is  in  no  way  diffi- 
cult, only  requiring  a  little  more  attention  than  the  first. 
The  alumina  thus  made  is  very  finely  divided.  The  reactions 
involved  are : 

2(AlF3.3NaF)  +  6CaO  =  AlA-sNa^O  +  6CaF,. 
2(AlFF3.3NaF)  +  AlA-sNa^O  +  6H,0  =  aCAlA-sH^O)  +  izNaF. 

During  the  last  operation  it  is  best  to  add  an  excess  of  cryo- 
lite, and  keep  the  liquid  in  motion  to  prevent  that  mineral  from 
caking  at  the  bottom.  Lead  is  the  best  material  to  make  these 
precipitating  tanks  of,  since  iron  would  contaminate  the  alumina. 
The  precipitate  is  washed  as  in  the  previous  operation.  The 
solution  of  sodium  fluoride  is  boiled  with  the  requisite  quantity 
of  burnt  lime,  which  converts  it  into  caustic  soda,  NaOH,  which 
is  separated  from  the  precipitated  calcium  fluoride  by  decanta- 
tion  and  washing. 

In  the  establishment  of  Weber,  at  Copenhagen,  where  at  one 
time  all  the  cryolite  produced  in  Greenland  was  received,  the 
mineral  was  decomposed  by  acid.  Hydrochloric  acid  attacks 
the  mineral  slowly,  but  sulphuric  acid  immediately  dissolves 
the  sodium  fluoride,  with  disengagement  of  hydrofluoric  acid ; 
gelatinous  aluminium  fluoride  separates  out,  and  is  attacked 
more  slowly.  The  cryolite  requires  nearly  i  ^  parts  of  sul- 
phuric acid  to  dissolve  it,  the  reaction  being : 

2(AlF3.3NaF)  +  6H2SO4  =  AlsCSO^s  +  3Na,S04+  12HF. 

The  solution  is  evaporated  and  crystallized,  when  the  sodium 
sulphate  crystallizes  out,  and  the  mother  liquid  is  treated  for  its 
alumina.  This  method  is  too  costly,  when  compared  with  more 
recent  processes,  to  be  used  at  present. 

According  to  Schuch*  very  finely-powdered  cryoHte  is  dis- 
solved by  a  large  excess  of  hot  dilute  soda  solution,  but  is 
thrown  down  unaltered  when  carbonic  acid  gas  is  passed  through 

*  Polytechnisches  Journal,  165,  p.  443. 


the  solution.  An  excess  of  concentrated  soda  liquor  converts 
the  mineral  into  sodium  aluminate  and  sodium  fluoride,  the  for- 
mer being  soluble  but  the  latter  almost  insoluble  in  the  soda 


The  Preparation  of  Aluminium  Chloride  and 
Aluminium-Sodium  Chloride. 

Anhydrous  aluminium  chloride  cannot  be  made  by  evap- 
orating the  solution  of  alumina  in  hydrochloric  acid,  for,  as  we 
have  seen,  decomposition  of  the  salt  sets  in,  hydrochloric  acid 
is  evolved  and  alumina  remains.  The  same  phenomena  occur 
on  evaporating  a  solution  of  the  double  chloride.  These  anhy- 
drous chlorides  are  prepared  by  a  method  discovered  by 
Oerstedt,  applicable  to  producing  a  number  of  similar  metallic 
chlorides,  which  consists  in  passing  a  current  of  dry  chlorine 
gas  over  an  ignited  mixture  of  alumina  and  carbon. 

Wohler*  proceeded  as  follows  in  preparing  the  aluminium 
chloride  which  was  used  in  his  early  experiments  :  "  Alumina  is 
mixed  with  charcoal  powder  and  made  plastic  with  oil.  Cylin- 
ders of  about  5  millimetres  diameter  are  made  of  this  paste, 
placed  in  a  crucible  with  charcoal  powder  and  heated  until  no 
more  combustible  gases  distil.  After  cooling  the  crucible  the 
cylinders  are  taken  out,  and  a  porcelain  or  glass  tube  open  at 
both  ends  filled  with  them.  This  is  then  placed  in  a  combus- 
tion furnace,  connected  at  one  end  with  a  chlorine  generator, 
and  at  the  other  with  a  tubular  extension  from  the  further  end 
of  which  the  gases  escape,  either  into  the  air  or  into  a  flask 
filled  with  milk  of  lime.  When  the  whole  apparatus  is  ready, 
and  filled  with  well-dried  chlorine  gas,  the  tube  is  heated  to 
glowing,  when  aluminium  chloride  is  formed  and  condenses  in 
the  extension  of  the  tube." 

Deville  paid  great  attention' to  the  production  and  purifica- 

*Pogg.  Ann.,  n,  p.  146. 



tion  of  aluminium  chloride ;  the  following  is  his  account  of  the 
processes  used  at  Javel : 

Manufacture  on  a  Small  Scale. — "  I  took  5  kilos  of  alumina 
and  mixed  it  with  2  kilos  of  carbon  and  a  little  oil ;  the  paste 
was  made  into  balls  and  ignited  at  a  bright-red  heat.  The 
compact,  coke-like  mass  resulting  was  broken  in  pieces  and 
put,  with  its  powder,  into  a  stoneware  retort,  C  (Fig.  5), 
having  a  capacity  of  about  10  litres,  and  terminating  in  a  neck. 

Fig.  s. 

D.  This  retort  was  put  in  a  furnace  and  heated  to  redness, 
while  a  current  of  dry  chlorine  gas  passed  in  by  the  tube  A. 
During  the  first  few  moments  considerable  quantities  of  water 
vapor  escape  from  the  neck.  When  aluminium  chloride  distils, 
as  is  shown  by  dense,  white  fumes,  a  porcelain  or  stoneware 
funnel,  E,  is  adjusted  to  the  neck  D,  and  kept  in  place  by  fill- 
ing the  joint  with  fine  asbestos  and  then  luting  it  over  with  a 
little  potter's  clay  mixed  with  hair.  Against  this  funnel  fits  a 
globular  vessel,  F,  the  joint  being  made  tight  in  a  similar  way. 
This  apparatus  condenses  and  holds  all  the  chloride  distilled. 
However  fast  the  chlorine  may  pass  into  the  retort,  it  is  so  well 
absorbed  during  three-fourths  of  the  operation  that  not  a  trace 
is  mixed  with  the  carbonic  oxide  escaping.  However,  the  gas 
always  fumes  a  little,  because  of  a  small  quantity  of  silicon 
chloride  being  formed  by  the  chlorine  and  carbon  attacking  the 
sides  of  the  retort,  or  from  chloride  of  sulphur  or  a  little  chlor- 


oxycarbonic  acid.  When  the  globe  F  is  filled  it  is  taken  away 
to  extract  the  coherent,  crystalline  aluminium  chloride  it  con- 
tains, and  is  replaced  immediately  by  another.  During  one 
operation  three  jars  were  thus  filled,  and  altogether  a  little  over 
lO  kilos  of  chloride  obtained.  In  the  retort  there  remained 
almost  a  kilo  of  coke  mixed  with  alumina  in  the  proportion  of 
two  of  carbon  to  one  of  alumina,  making  330  grammes  of  the 
latter  remaining  unattacked  out  of  S  kilos.  This  coke  contains 
also  some  double  chloride  of  alumina  and  potassium  and  a  little 
calcium  chloride,  which  render  it  deliquescent.  This  residue 
was  washed,  mixed  with  a  fresh  quantity  of  alumina,  and  em- 
ployed in  a  new  operation." 

Manufacture  on  a  large  scale. — "  In  applying  this  process  on 
a  large  scale,  the  oil  and  carbon  were  replaced  by  tar,  the 
alembic  by  a  gas-retort,  and  the  glass  receiver  by  a  small  brick 
chamber  lined  with  glazed  tiles.  The  alumina  was  obtained  by 
calcining  ammonia  alum  in  iron  pots ;  the  residue  obtained  by 
one  calcination  at  a  bright-red  heat  was  mixed  with  pitch,  to 
which  a  little  charcoal  dust  was  added.  The  paste  was  well 
mixed,  introduced  into  iron  pots,  covered  carefully  and  heated 
until  all  vapors  of  tar  ceased  burning.  The  aluminous  carbon 
is  used  while  it  is  still  hot,  if  possible,  as  it  is  quite  hygroscopic. 
(This  aluminous  carbon  conducts  electricity  wonderfully  well ; 
it  is  the  best  electrode  to  use  in  making  aluminium  by  the  bat- 
tery, since  its  alumina  regenerates  the  bath.)  The  residue  is 
hard,  porous,  and  cracked,  and  contains  sulphur  from  the  sul- 
phuric acid  of  the  alum,  a  little  iron,  phosphoric  acid  in  small 
quantity,  a  perceptible  proportion  of  lime,  and  finally  potash, 
which  is  always  present  in  alums  made  from  clay.  The  chlo- 
rine gas  used  was  conducted  by  lead  pipes  and  passed  over 
calcium  chloride  before  being  used.  The  retort  used  was  of 
about  300  litres  capacity,  and  was  placed  vertically  in  a  sort  of 
chimney,  C  (Fig.  6),  the  flame  circulating  all  around  it.  In 
the  bottom  was  a  square  opening,  x,  about  20  centimetres 
square,  which  could  be  closed  by  a  tile  kept  in  place  by  a  screw, 
V.     A  porcelain  tube  pierced  the  sides  of  the  furnace  and  en- 



tered  the  retort  at  O;  it  was  protected  from  the  flame  by  a  fire- 
clay cyHnder  inclosing  it.  At  the  top,  the  retort  was  closed  by 
a  tile,  Z,  of  refractory  brick,  in  the  centre  of  which  was  made 
a  square  opening,  W,  oi  \o  \.o  \2  centimetres  side.  Finally,  an 
opening,  X,  placed  30  centimetres  below  the  plate  Z,  gave 
issue  to  the  vapors  distilled,  conducting  them  into  the  chamber 
L.  This  condensation  chamber  was  about  i  metre  cube ;  it  had 

Fig.  6. 

one  wall  of  bricks  in  common  with  the  furnace,  thus  keeping 
it  rather  hot.  The  other  walls  should  be  thin  and  set  with 
close  joints  and  very  little  mortar.  The  cover,  M,  was  mov- 
able ;  it  and  the  sides  of  the  chamber  were  of  glazed  tiles.  An 
opening  20-30  centimetres  square  in  the  lower  part  of  the 
chamber  communicated  with  flues  lined  with  lead,  for  a  little 
chloride  was  drawn  into  them.  The  uncondensed  gas  passed 
to  a  chimney. 

"  To  work  such  an  apparatus  it  is  necessary,  first  of  all,  to 
dry  it  with  the  greatest  care  in  all  its  parts,  especially  the  con- 
densation   chamber.     The  retort  is  slowly  heated  and  is  left 


Open  at  Z  until  it  is  judged  quite  dry,  and  is  then  filled  with 
red-hot,  freshly-calcined  mixture  of  carbon  and  alumina.  The 
top  cover  is  then  replaced,  and  the  fire  urged  until  the  retort  is 
at  a  dark-red  heat  all  over.  Finally,  chlorine  is  passed  in,  but 
the  opening  at  W  is  kept  open ;  the  gas  is  allowed  to  pass  into 
the  condensation  chamber  only  when  fumes  of  aluminium 
chloride  appear  very  abundantly  at  W.  When  the  operation 
proceeds  right,  almost  all  the  aluminium  chloride  is  found  at- 
tached in  a  dense,  solid  mass  to  the  cover  M.  I  have  taken 
out  at  one  time  a  plate  weighing  almost  50  kilogrammes,  which 
was  less  than  10  centimetres  thick;  it  was  made  up  of  a  large 
number  of  sulphur-yellow  crystals  penetrating  each  other  and 
looking  like  stalactites  and  long  soda  crystals.  When  it  is 
judged  that  the  material  in  the  retort  is  almost  exhausted,  the 
hole  X  is  opened,  the  residue  scraped  out,  and  fresh  mixture 
put  in.  During  the  operation  there  should  be  no  white  vapors 
coming  from  the  condensation  chamber,  but  the  odor  of  gas 
will  always  be  sharp  because  of  the  silicon  chloride  present, 
formed  unavoidably  by  the  chlorine  attacking  the  retort.  A 
gas  retort,  handled  well,  should  last  continuously  two  or  three 
months,  or  even  more.  The  furnace  should  be  constructed  so 
as  to  permit  its  easy  replacement  without  much  expense. 
When  in  use,  the  retort  is  closely  watched  through  spy-holes  in 
the  wall,  and  any  cracks  which  may  appear  promptly  plastered 
up,  if  not  large,  with  a  mixture  of  fine  asbestos  and  soda 

Purification  of  aluminium  chloride. — "  It  often  happens  that 
the  chloride  obtained  is  not  pure,  either  from  the  nature  of  the 
apparatus  employed,  or  from  neglect  of  the  many  precautions 
which  should  be  taken.  In  this  case,  to  purify  it,  it  is  heated 
in  an  earthen  or  cast-iron  vessel  with  fine  iron  turnings.  When 
the  hydrochloric  acid,  hydrogen  and  permanent  gases  are 
driven  from  the  apparatus,  it  is  closed  and  heated  hotter,  which 
produces  a  light  pressure  under  which  influence  the  aluminium 
chloride  melts  and  enters  into  direct  contact  with  the  iron. 
The  ferric  chloride,  which  is  as  volatile  as  aluminium  chloride. 


is  transformed  into  ferrous  chloride,  which  is  much  less  volatile, 
and  the  aluminium  chloride  can  be  obtained  pure  by  being 
volatilized  away  or  distilled  in  an  atmosphere  of  hydrogen." 

When  the  processes  just  described  were  put  in  use  at  the 
chemical  works  at  La  Glaciere,  great  care  had  to  be  taken  to 
avoid  letting  vapors  and  acid  gases  escape  into  the  air,  since 
the  works  were  surrounded  by  dwellings.  To  avoid  these  in- 
conveniences, the  vapor  of  aluminium  chloride  was  made  to 
enter  a  heated  space  in  which  was  sodium  chloride,  in  order  to 
produce  the  less  volatile  double  chloride;  but  the  apparatus 
choked  up  so  persistently  that  the  attempt  was  given  up.  It 
then  occurred  to  Deville  to  put  sodium  chloride  into  the  mix- 
ture itself  in  the  retort.  The  same  apparatus  was  used  as  be- 
fore, except  that  the  large  gas-retort  had  to  be  replaced  by  a 
smaller  earthen  one,  which  could  be  heated  much  hotter,  the 
grate  being  carried  half  way  up  the  retort.*  The  condensation 
chamber  had  to  be  replaced  by  a  small  earthen  vessel.  The 
double  chloride  produced  is  fusible  at  about  200°,  and  is  quite 
colorless  when  pure,  but  colored  yellow  by  iron.  It  is,  more- 
over, very  little  altered  in  dry  air  when  in  compact  masses,  and 
can  be  easily  handled.  When  the  double  chloride  is  obtained 
quite  pure,  it  gives  up  its  aluminium  completely  when  reduced 
by  sodium. 

The  following  description  by  M.  Margottetf  will  show  the 
form  of  apparatus  used  in  1882  by  the  French  company  carry- 
ing on  the  Deville  process  at  Salindres : — 

The  double  chloride  may  be  obtained  in  the  same  manner  as 
the  simple  chloride ;  it  is  sufficient  to  put  some  common  salt, 
NaCl,  into  a  mixture  of  alumina  and  carbon,  and  on  heating 
this  mixture  strongly  there  is  formed,  by  the  action  of  the 
chlorine,  aluminium-sodium  chloride,  which  distils  at  a  red  heat 
and  condenses  in  a  crystalline  mass  at  about  200°.     The  hy- 

*  It  was  when  first  using  this  process  that  Deville  borrowed  some  zinc  retorts  from 
the  Vielle  Montagne  works,  and  since  they  contained  a  little  zinc  in  their  composition 
the  aluminium  made  for  a  while  was  quite  zinciferous. 

t  Fremy's  Ency.  Chimique. 



drated  alumina  obtained  in  the  preceding  operation  is  mixed 
witli  salt  and  finely  pulverized  charcoal,  in  proper  proportions, 
the  whole  is  sifted,  and  a  mixture  produced  as  homogeneous 
as  possible ;  then  it  is  agglomerated  with  water  and  made  into 
balls  the  size  of  the  fist.  These  balls  are  first  dried  in  a  drying 
stove,  at  about  150°,  then  calcined  at  redness  in  retorts,  where 
the  double  chloride  should  commence  to  be  produced  just  as 
the  balls  are  completely  dried.  These  retorts  are  vertical  cyl- 
inders of  refractory  earth ;  each  one  is  furnished  with  a  tube  in 
its  lower  part  for  the  introduction  of  chlorine,  and  with  another 
towards  its  upper  end  for  the  exit  of  the  vapor  of  double  chlo- 
ride (see  Fig.  7).     A  lid  carefully  luted  during  the  operation 

Fig.  7. 

with  a  mixture  of  fine  clay  and  horse-dung  serves  for  the  charg- 
ing and  discharging  of  the  retort.  The  double  chloride  is  con- 
densed in  earthen  pots  like  flower-pots,  made  of  ordinary  clay, 
and  closed  by  a  well-luted  cover,  into  which  passes  a  pipe  of 
clay  to  conduct  the  gas  resulting  from  the  operation  into  flues 
connected  with  the  main  chimney.  Each  retort  is  heated  by  a 
fire,  the  flame  of  which  circulates  all  round  it,  and  permits 
keeping  it  at  a  bright  red  heat.  An  operation  is  conducted  as 
follows :  The  retort  is  filled  with  stove-dried  balls,  the  lid  is 


carefully  luted,  and  the  retort  is  heated  gently  till  all  the  mois- 
ture is  driven  off.  This  complete  desiccation  is  of  great  im- 
portance, and  requires  much  time.  Then  chlorine,  furnished 
by  a  battery  of  three  generating  vessels,  is  passed  in.  During 
the  first  hours,  the  gas  is  totally  absorbed  by  the  balls ;  the 
double  chloride  distils  regularly  for  about  three  hours,  and  runs 
into  the  earthen  pots,  where  it  solidifies.  Toward  the  end,  the 
distillation  is  more  difficult  and  less  regular,  and  the  chlorine  is 
then  only  incompletely  absorbed.  After  each  operation  there 
remains  a  little  residue  in  the  retort,  which  accumulates  and  is 
removed  every  two  days,  when  two  operations  are  made  per 
day.  One  operation  lasts  at  least  twelve  hours,  and  a  retort 
lasts  sometimes  a  month.  The  double  chloride  is  kept  in  the 
pots  in  which  it  was  condensed  until  the  time  it  is  to  be  used 
in  the  next  operation  ;  it  is  almost  chemically  pure,  save  traces 
of  iron,  and  is  easy  to  keep  and  handle. 

The  following  estimate  was  made  by  Wurtz,  in  1872,  show- 
ing the  cost  of  a  kilo  of  aluminium-sodium  chloride  as  made 
by  the  above  process:  — 

Anhydrous  alumina  0.59  kilos  @  86  fr.  per  100  kilos  =  o  it.  50.7  cent. 
Manganese  dioxide  3.74     "      "    14  "     "      "       "      =  o "    52.3     " 
Hydrochloric  acid  15.72    "      "     3"    "      "      "     =0"   47.1     " 

Coal 25.78     "      "      1.40 '      =0"    36.1     " 

Wages o"   23.8    " 

Expenses o "    38.0     " 

Total 2  fr.  48.0  cent. 

This  is  equal  to  about  22^  cents  per  pound.  An  average 
of  10  kilos  of  this  was  used  to  produce  one  kilo  of  aluminium, 
which  shows  a  yield  of  only  70  per  cent,  of  the  contained  alu- 
minium, and  an  increased  cost  of  6y  cents  on  every  pound  of 
aluminium  from  the  imperfection  of  reduction.  In  this  respect 
there  certainly  seems  large  room  for  improvement. 

The  largest  plant  ever  erected  for  the  manufacture  of  alu- 
minium-sodium chloride  was  that  of  the  Aluminium  Co.  Ltd., 
at  Oldbury,  near  Birmingham,  England.  The  plant  was  com- 
menced in  the  latter  part  of  1887,  and  was  in  working  order  in 


July,  1888.  The  process  is  in  principle  indentical  with  that  used 
at  Salindres,  but  the  whole  was  on  such  a  large  scale  that  the 
description  is  still  interesting. 

Twelve  large  regenerative  gas  furnaces  are  used,  in  each  of 
which  are  placed  five  horizontal  fire-clay  retorts  about  10  feet 
in  length,  into  which  the  mixture  is  placed.  These  furnaces  are 
in  two  rows,  of  six  each,  along  each  side  of  a  building  about 
250  feet  long,  leaving  a  clear  passage  down  the  centre  50  feet 
wide.  Above  this  central  passage  is  a  platform  swung  from 
the  roof,  which  carries  the  large  lead  mains  to  supply  chlorine 
to  the  retorts ;  opposite  each  retort  is  a  branch  pipe  controlled 
by  a  valve.  The  valves  are  designed  so  that  the  chlorine  must 
pass  through  a  certain  depth  of  (non-aqueous)  liquid,  thus 
regulating  the  flow  and  preventing  any  back  pressure  in  the  re- 
tort from  forcing  vapor  into  the  main.  The  opposite  or  back 
ends  of  the  retorts  are  fitted  with  pipes  which  convey  the  vapor 
of  the  double  chloride  into  cast-iron  condensers  and  thence  into 
brick  chests  or  boxes,  the  outsides  or  ends  of  which  are  closed 
by  wooden  doors  fitting  tightly.  Convenient  openings  are  ar- 
ranged for  clearing  out  the  passages,  which  may  become 
choked  because  of  the  quickness  with  which  the  double  chlor- 
ide condenses.  On  looking  down  the  centre  of  the  building  it 
presents  the  appearance  of  a  double  bank  of  gas  retorts  for 
making  ordinary  illuminating  gas,  except  that  the  retorts  are 
only  one-high.     (Fig.  8). 

The  chlorine  plant  is  on  a  correspondingly  large  scale,  the 
usual  manganese-dioxide  method  being  employed  and  the  spent 
liquor  regenerated  by  Weldon's  process.  The  chlorine  gas  is 
stored  in  large  gasometers  from  which  it  is  supplied  to  the  re- 
torts at  a  certain  pressure.  The  mixture  for  treatment  is  made 
by  mixing  hydrated  alumina  with  common  salt  and  carbon  in 
the  form  of  charcoal  powder  or  lamp-black.  This  being  well 
mixed  is  moistened  with  water,  thrown  into  a  pug-mill  from 
which  it  is  forced  out  as  solid  cylinders,  and  cut  into  about  3 
inch  lengths  by  a  workman.  The  lumps  are  then  piled  on  top 
of  the  large  chloride  furnaces  to  dry.     In  a  few  hours  they  are 



hard  enough  to  allow  handling,  and  are  put  into  large  wagons 
and  wheeled  to  the  front  of  the  retorts. 

When  the  retorts  are  at  the  proper  temperature  for  charging, 
the  balls  are  thrown  in  until  the  retort  is  quite  full,  the  fronts 
are  then  put  up  and  luted  tightly  with  clay,  and  the  charge  left 
alone  for  about  four  hours,  during  which  the  water  of  the  hy- 
drated  alumina  is  completely  expelled,  the  rear  end  of  the  re- 
tort being  disconnected  from  the  condensing   chamber,  which 

Fig.  8. 

must  be  kept  perfectly  dry,  and  connected  directly  with  the 
chimney.  At  the  end  of  this  time  the  chlorine  is  turned  on 
and  the  retort  connected  with  the  receiver.  At  first  the  chlo- 
rine passed  in  is  all  absorbed  by  the  charge  and  only  carbonic 
oxide  escapes  into  the  boxes,  where  it  is  ignited  and  burns, 
thus  warming  them  up.  After  a  certain  time  dense  fumes  are 
evolved,  and  then  the  condensers  are  shut  tightly  and  the  un- 
condensed  gases  pass  into  the  chimney.  The  chlorine  is  passed 
in  for  72  hours  in  varying  quantity,  the  boxes  at  the  rear  being 
opened  from  time  to  time  by  the  workmen  to  note  the  pro- 
gress of  the  distillation.  The  greater  part  of  the  double  chlo- 


ride  liquefies  and  trfckles  down  to  the  floor  of  the  chambers, 
but  a  portion  sublimes  and  condenses  on  the  walls  as  a  yellow 
crystalline  powder.  These  chambers  are  emptied  from  time  to 
time  and  the  contents  packed  away  in  air-tight  wooden  chests, 
that  it  may  keep  without  absorbing  moisture  from  the  air.  At 
the  end  of  the  distillation  the  chlorine  valves  are  closed  and 
the  condenser  boxes  cleaned  out ;  the  retorts  are  also  opened 
at  their  front  end  and  the  residue  raked  out.  This  residue 
consists  of  a  small  quantity  of  alumina,  charcoal  and  salt,  and 
is  remixed  in  certain  proportions  with  fresh  material  and  used 
over  again.  The  retorts  are  then  immediately  re-charged  and 
the  operations  repeated.  Each  set  of  five  retorts  produces 
about  1600  to  1800  lbs.  in  one  operation,  or  say  3500  lbs.  per 
week.  The  twelve  furnaces  are  therefore  capable  of  producing 
easily  1,500,000  lbs.  of  double  chloride  per  annum.  Since  10 
lbs.  of  this  salt  are  required  to  produce  i  lb.  of  aluminium,  the 
capacity  of  the  works  is  thus  seen  to  be  150,000  lbs.  or  over  of 
metal  per  year. 

This  last  remark  as  to  the  proportion  of  chloride  required  to 
form  the  metal  will  show  the  absolute  necessity  there  is  to  keep 
iron  from  contaminating  the  salt.  This  gets  in,  in  varying  pro- 
portions, from  the  iron  in  the  materials  used  and  in  the  fire-clay 
composing  the  retort,  and  exists  as  ferrous  and  ferric  chlorides. 
Exercising  the  utmost  care  as  to  the  purity  of  the  alumina  and 
charcoal  used,  and  after  having  the  retorts  made  of  a  special 
fire-clay  containing  a  very  small  percentage  of  iron,  it  was  found 
impossible  to  produce  a  chloride  on  a  large  scale  containing  less 
than  0.3  per  cent,  of  iron.  This  crude  chloride  is  highly  de- 
liquescent and  varies  in  color  from  light  yellow  to  dark  red — 
the  color  depending  not  so  much  on  the  absolute  amount  of 
iron  present  as  on  the  proportion  of  iron  present  as  ferric  salt, 
which  has  a  high  color.  Since  practically  all  the  iron  present 
in  the  salt  passes  into  the  aluminium,  it  is  seen  that  the  latter 
would  contain  3  per  cent,  or  more  of  iron.  For  some  time  the 
only  way  to  obviate  this  difficulty  was  to  resort  to  purifying  the 
aluminium,  by  which  the  content  of  iron  was  finally  reduced  to 


2  per  cent.  Mr.  Castner  has  since  perfected  a  process  for 
purifying  the  double  chloride  by  which  only  o.oi  per  cent,  of 
iron  is  left  in  it.  The  principle  employed  in  doing  this  is  de- 
scribed in  the  patent  claims*  to  be  the  reduction  of  the  iron  salts 
to  metallic  iron  by  melting  the  chloride  (single  or  double)  with 
a  quantity  of  metallic  aluminium  or  sodium  sufiScient  for  this 
purpose.  The  purified  chloride  is  quite  white  and  far  less  de- 
liquescent than  the  crude  salt,  which  seems  to  indicate  that  the 
iron  chlorides  have  a  large  share  in  rendering  the  crude  salt  so 
deHquescent.  The  purified  chloride  is  preserved  by  melting 
and  running  into  tight  iron  drums.  A  process  of  purification 
used  later  by  Mr.  Castnerf  consisted  in  separating  out  the  iron 
electrolytically.  The  melted  salt  was  passed  slowly  along  a 
trough  on  the  sides  of  which  were  electrodes  kept  at  a  tension 
sufficient  to  decompose  the  iron  chlorides,  the  tension  also 
being  gradually  decreased  from  one  end  to  the  other  propor- 
tionally to  the  decreasing  quantity  of  iron  in  the  material  as  it 
passed  along. 

The  success  of  the  manufacture  of  the  double  chloride  is  said 
to  depend  on  the  proportions  of  the  mixture,  the  temperature 
of  the  furnace,  the  quantity  of  chlorine  introduced,  and  the  de- 
tails of  construction  of  the  retorts ;  but  very  little  information 
on  these  points  has  been  made  public.  The  following  figures 
may  give  some  idea  of  the  quantities  of  materials  used :  The 
production  of  1000  lbs.  of  double  chloride  is  said  to  require — 

Common  salt 357  lbs. 

Hydrated  alumina 491    " 

Chlorine  gas 674    " 

Coal 1800    " 

The  salt  and  hydrated  alumina  are  therefore  mixed  in  about 
the  same  proportion  as  those  indicated  by  the  formula  which 
represents  the  reaction 

*U.  S.  Patent,  No.  409,668,  Aug.  27,  1889. 
tU.  S.  Patent,  No.  422,500,  March  4,  1890. 



for  if  we  assume  the  hydrated  alumina  used  to  contain  90  per 
cent,  of  that  compound,  the  491  lbs.  of  it  used  would  corres- 
pond to  very  nearly  the  amount  of  salt  said  to  be  used.  As 
to  the  cost  of  this  double  chloride,  so  many  uncertain  elements 
enter  into  it  that  it  cannot  be  satisfactorily  estimated  from  the 
data  at  hand.  We  are  informed,  however,*  that  the  double 
chloride  used  represented  43  per  cent,  of  the  cost  of  aluminium 
to  this  company.  If  we  place  the  total  cost  at  8  shillings  per 
lb.  this  would  indicate  a  trifle  over  4  pence  per  lb.  as  the  cost 
of  the  double  chloride.     It  was  probably  not  over  3  pence. 

H.  A.  Gadsden,!  of  London,  patented  a  method  of  obtaining 
aluminium,  in  which  the  aluminium  chloride  used  is  obtained  by 
a  method  similar  in  all  respects  to  the  process  as  described  by 
Deville,  except  that  the  corundum  or  bauxite  used  is  mixed 
with  about  10  per  cent,  of  sodium  or  potassium  fluoride  and  a 
small  quantity  of  fluorspar.  After  this  has  been  mixed  and 
calcined  it  is  pulverized,  10  per  cent,  of  charcoal  dust  added, 
made  into  balls  and  heated  in  a  muffle  until  pasty.  Taken 
out  of  the  muffle  they  are  then  put  into  a  retort,  heated  highly, 
and  chlorine  gas  passed  over  them,  when  aluminium  chloride 

Count  R.  de  Montgelas|  patents  a  process  for  producing 
aluminium  chloride  and  the  double  chloride  with  sodium,  in  • 
which  the  only  difference  from  the  preceding  methods  is  that 
molasses  is  used  instead  of  pitch  for  moulding  the  mixture  into 
balls,  the  mixture  otherwise  containing  alumina,  charcoal,  and 
sodium  chloride ;  and  it  is  claimed  that  by  regulating  the  heat 
at  which  chlorine  is  passed  over  this  mixture,  previously  cal- 
cined, aluminium  chloride  can  be  volatilized  while  aluminium- 
sodium  chloride  remains  in  the  retort.  The  use  of  horizontal 
retorts  is  recommended. 

*Zeitschrift  des  Verein  Deutscher  Ingenieure,  1889,  p.  301. 

t  German  Patent  (D.  R.  P.)  No.  27,572  (1884). 

I  English  Patents  Nos.  10,011,  10,012,  10,013,  Aug.  4,  1886. 


Prof.  Chas.  F.  Mabery,*  of  the  Case  School  of  Applied  Sci- 
ence, Cleveland,  patented  and  assigned  to  the  Cowles  Bros,  the 
process  of  making  aluminium  chloride,  consisting  in  passing 
dry  chlorine  or  hydrochloric  acid  gas  over  an  alloy  of  alumin- 
ium and  some  other  metal  kept  in  a  closed  vessel  at  a  temper- 
ature sufficient  to  volatilize  the  aluminium  chloride  formed, 
which  is  caught  in  a  condenser.  Or,  hydrochloric  acid  gas  is 
passed  through  an  electrically  heated  furnace,  in  which  alumina 
is  being  decomposed  by  carbon,  a  condenser  being  attached  to 
the  opposite  end  of  the  furnace. 

Mr.  Paul  Curiej  states  that  aluminium  chloride  can  be  made 
by  passing  vapors  of  carbon  disulphide  and  hydrochloric  acid 
either  simultaneously  or  successively  over  ignited  alumina  or 
clay.  The  first  forms  aluminium  sulphide,  which  the  latter 
converts  into  the  volatile  chloride,  which  distils. 

H.  W.  WarrenI  recommends  the  following  process  as  of  gen- 
eral application  in  producing  anhydrous  metallic  chlorides. 
Petroleum  is  saturated  with  either  chlorine  or  hydrochloric  acid 
gas,  both  gases  being  soluble  in  it  to  a  large  extent,  particu- 
larly the  latter  gas.  This  operation  is  performed  at  a  low  tem- 
perature, as  more  of  the  gases  is  then  dissolved.  The  oxide  of 
the  metal,  alumina,  for  instance,  is  put  into  large  earthenware 
retorts,  and  raised  to  red  heat.  The  saturated  oil  is  then  boiled 
and  its  vapor  passed  into  the  retort.  On  contact  with  the 
oxide  a  strong  reaction  commences,  fumes  of  aluminium  chlor- 
ide are  at  once  evolved,  and  distil  into  a  condenser,  the  opera- 
tion being  continued  until  no  more  white  fumes  appear.  Then 
fresh  alumina  is  supplied,  and  the  reaction  continues.  The 
aluminium  chloride  may  be  purified  from  any  oil  by  gentle  ap- 
plication of  heat.  Mr.  Warren  also  used  naphthaline  chloride 
with  advantage,  as  also  chloride  of  carbon,  but  their  high  price 
rendered  them  unable  to  compare  with  petroleum  in  economy. 

*  U.  S.  Patent,  Oct.  26,  1886. 
t  Chemical  News,  1873,  p.  307. 
J  Chemical  News,  April  29,  1887. 


Aluminium  bromide  can  be  similarly  prepared  by  substituting 
bromine  for  chlorine. 

Camille  A.  Faure,  of  New  York,  the  well-known  inventor  of 
the  Faure  storage  battery,  has  patented*  a  process  for  produc- 
ing aluminium  chloride,  which  is  very  similar  to  the  above 
method.  The  manipulation  is  described  as  follows :  An  oxy- 
genated ore  of  aluminium  is  brought  to  about  a  red  heat  by 
bringing  it,  in  a  furnace,  into  direct  contact  with  the  flame. 
When  at  proper  heat  the  flame  is  cut  off  and  a  gas  containing 
carbon  and  chlorine  introduced.  A  mixture  of  petroleum  vapor 
or  a  similar  hydrocarbon  with  hydrochloric  acid  gas  is  pre- 
ferred. Vaporized  chloride  of  aluminium  immediately  passes 
off  into  a  condenser. 

In  a  paper  written  by  Mr.  Faure,  and  read  before  the  French 
Academy  of  Sciences  by  M.  Berthelot,t  it  was  stated  that  the 
aim  of  this  process  was  to  suppress  the  prominent  disadvant- 
ages of  the  older  methods :  viz.,  cost  and  wear  and  tear  of  re- 
torts, great  consumption  of  fuel,  slowness  of  the  operation, 
large  amount  of  labor,  and  cost  of  the  chlorine.  For  this  pur- 
pose the  chlorine  is  replaced  by  hydrochloric  acid  gas  and  the 
carbon  by  a  hydrocarbon.  Since  all  pure  hydrocarbons  are 
decomposed  at  a  red  heat  with  deposition  of  carbon,  the  pro- 
cess would  appear  impracticable ;  but  a  proper  mixture  of  hy- 
drochloric acid  gas  and  naphthaline  vapor  is  said  not  to  de- 
compose by  the  highest  temperature  alone,  a  new  compound 
being  formed,  a  sort  of  napthaline  chloride,  which  is  exceed- 
ingly corrosive  and  powerful  enough  to  attack  any  oxide  and 
convert  it  into  chloride.  To  carry  out  the  process  a  gas  fur- 
nace with  large  bed  is  used.  On  this  is  spread  a  layer  of  small 
pieces  of  bauxite  about  two  feet  deep.  The  flame  comes  in 
over  the  ore,  passes  downward  through  it  and  through  numer- 
ous holes  arranged  in  the  hearth,  and  thence  to  a  chimney.  In 
this  way  the  heat  of  the  gases  is  well   utilized,  while  the  layer 

*  U.  S.  Patent,  No.  385,345,  July  3,  1888. 
t  July  30,  1888. 


of  bauxite  is  heated  to  whiteness  on  top  and  to  low-red  at  the 
bottom.  The  flames  are  then  turned  off  and  the  mixture  of 
naphthaHne  and  hydrochloric  acid  vapors  passed  upward 
through  the  bed,  and  by  their  reaction  producing  aluminium 
chloride,  which  is  diverted  by  suitable  flues  into  a  condenser. 
It  is  claimed  that  by  careful  fractional  condensation  the  chlor- 
ides of  silicon,  iron,  calcium,  etc.,  formed  from  impurities  in 
the  bauxite,  can  be  easily  separated,  that  of  silicon  being 
more  volatile  and  those  of  iron  and  calcium  less  volatile  than 
aluminium  chloride.  As  naphthaline  is  a  bye-product  from 
gas-works,  it  is  claimed  that  it  can  be  bought  for  i  ^  cents  per 
lb.,  and  that  only  j^  oi  a  lb.  is  used  per  lb.  of  aluminium  chlo- 
ride produced.  It  is  also  claimed  that  one  furnace,  with  two 
men  to  work  it,  will  produce  4000  lbs.  of  chloride  a  day.  The 
estimated  cost  of  the  chloride  is  about  i  }4  cents  per  pound,  of 
which  17  per  cent,  is  for  beauxite,  47  per  cent,  for  hydrochloric 
acid,  27  per  cent,  for  naphthaline,  and  9  per  cent,  for  labor. 
Mr.  Faure  experimented  in  the  vicinity  of  New  York  during 
1889,  and  was  sanguine  of  having  the  process  at  work  in  1890, 
but  no  commercial  process  has  resulted  from  these  efforts. 
(See  further.  Chap.  XI.) 

In  all  the  processes  for  producing  aluminium  chloride  so  far 
considered,  the  use  of  common  clay  was  not  recommended, 
since  silicon  chloride  is  formed  as  well  as  aluminium  chloride. 
The  only  method  proposed  for  using  clay  for  this  purpose  is 
that  of  M.  Dullo,  nearly  twenty  years  ago,  and  which  cannot 
have  been  very  successful,  since  it  has  not  been  heard  of  in 
operation.  We  will  repeat  his  remarks,  however,  for  there  is 
still  a  large  field  open  in  the  utilization  of  clay  for  the  manu- 
facture of  aluminium,  and  since  the  metal  is  becoming  so  cheap 
the  manufacturers  are  not  above  looking  for  and  utilizing  the 
cheapest  raw  material  available. 

* "  Aluminium  chloride  may  be  obtained  easily  by  direct 
treatment  of  clay.  For  this  purpose  a  good  clay,  free  from  iron 
and  sand,  is  mixed  with  enough  water  to  make  a  thick  pulp, 

*  Bull,  de  la  Soc.  Chem.,  i860,  vol.  v.,  p.  472. 


to  which  are  added  sodium  chloride  and  pulverized  carbon. 
For  every  lOO  parts  of  dry  clay  there  are  taken  I20  parts  of 
salt  and  30  of  carbon.  The  mixture  is  dried  and  broken  up 
into  small  fragments,  which  are  then  introduced  into  a  red-hot 
retort  traversed  by  a  current  of  chlorine.  Carbonic  oxide  is 
disengaged,  while  at  the  same  time  aluminium  chloride  and  a 
little  silicon  chloride  are  formed.  It  is  not  necessary  that  the 
chlorine  should  be  absolutely  dry,  it  may  be  employed  just  as 
it  comes  from  the  generator.  The  gas  is  absorbed  very  rapidly, 
because  between  the  aluminium  and  silicon  there  are  reciprocal 
actions  under  the  influence  of  which  the  chemical  actions  are 
more  prompt  and  energetic.  The  aluminium  having  for  chlo- 
rine a  greater  afifinity  than  silicon  has,  aluminium  chloride  is 
first  formed,  and  it  is  only  when  all  the  aluminium  is  thus  trans- 
formed that  any  silicon  chloride  is  formed.  When  the  latter 
begins  to  form  the  operation  is  stopped,  the  incandescent  mix- 
ture is  taken  out  of  the  retort  and  treated  with  water.  The 
solution  is  evaporated  to  dryness  to  separate  out  a  small  quan- 
tity of  silica  which  is  in  it,  the  residue  is  taken  up  with  water, 
and  aluminium-sodium  double  chloride  remains  when  the 
filtered  solution  is  evaporated  to  dryness." 

We  must  say  of  M.  Dullo's  suggestions  that  it  is  the  general 
experience  that  the  more  volatile  silicon  chloride  is  formed 
first;  it  is  also  very  improbable  that  a  solution  of  aluminium- 
sodium  chloride  can  be  evaporated  without  decomposition. 


The  Preparation  of  Aluminium  Fluoride  and 
Aluminium-Sodium  Fluoride  (Cryolite). 

Natural  cryolite  is  too  impure  for  use  in  many  operations 
which  aim  to  produce  very  pure  aluminium.  Schuh  has  pro- 
posed boiling  the  mineral  in  solution  of  soda.  Under  certain 
conditions  sodium  aluminate  is  formed  (see  p.  JJI),  but  if  the 
solution  of  soda  is  dilute  the  liquor  remains  clear  after  taking 
up  the  cryolite,  and  on  passing  a  current  of  carbonic  acid  gas 


through  it  aluminium-sodium  fluoride  is  precipitated.  In  this 
way  the  pure  double  fluoride  can  be  separated  from  impure 

Berzelius  recommended  preparing  artificial  cryolite  by  de- 
composing aluminium  hydrate  by  a  solution  of  sodium  fluoride 
and  hydrofluoric  acid,  the  hydrate  being  added  to  the  liquid 
until  its  acidity  was  just  neutralized  : — 

A1,03.3H,0  +  6NaF  +  6HF  =  2(AlF3.3NaF)  +  6H,0. 

Deville  states  that  on  adding  sodium  chloride  to  a  solution 
obtained  by  dissolving  alumina  in  an  excess  of  hydrofluoric 
acid,  a  precipitate  of  cryolite  is  obtained.  Since  cryolite  is 
hardly  attacked  at  all  by  hydrochloric  acid,  it  is  probable  that 
the  reaction  occurring  is 

AIF3  +  3HF  +  sNaCl  =  AlFa.sNaF  +  3HCI. 

The  process  which  Deville  recommended  as  best,  however,  is 
the  treatment  of  a  mixture  of  calcined  alumina  and  carbonate 
of  soda,  mixed  in  the  proportions  in  which  their  bases  exist  in 
cryolite,  by  an  excess  of  pure  hydrofluoric  acid : — 

AliiOa  -I-  sNa/'Os  +  i2HF=2(AlF.3NaF)  -|-  3CO2  +  6H2O. 

100  parts  of  pure  alumina  requiring  310  parts  of  sodiurri  car- 
bonate and  245  of  anhydrous  hydrofluoric  acid,  there  being 
410  parts  of  cryolite  formed.  On  drying  the  mass  and  melting 
it  there  results  a  limpid,  homogeneous  bath  having  all  the 
characteristics  of  cryolite,  being  reduced  by  sodium  or  by  an 
electric  current,  which  would  not  result  from  a  mere  mixture  ot 
alumina  and  sodium  fluoride  melted  together. 

Deville  also  states  that  when  anhydrous  aluminium  chloride 
is  heated  with  sodium  fluoride  in  excess,  a  molten  bath  results 
of  great  fluidity,  and  on  cooling  and  dissolving  away  the  excess 
of  sodium  fluoride  by  repeated  washings  the  residue  is  similar 
to  cryolite,  while  the  solutions  contain  no  trace  of  any  soluble 
aluminium  salt: — 

AICI3  +  6NaF=AlF3.3NaF  4-  sNaCl. 


It  is  evident,  however,  that  the  above  reaction  would  be  the 
reverse  of  a  profitable  one,  and  is  therefore  not  of  economical 

Pieper*  patents  a  very  similar  reaction,  but  operates  in  the 
wet  way.  A  solution  of  aluminium  chloride  is  decomposed  by 
adding  to  it  a  suitable  quantity  of  sodium  fluoride  in  solution. 
Sodium  chloride  is  formed  and  cryolite  precipitated,  as  in  the 
last  reaction  given.  By  adding  different  proportions  of  sodium 
fluoride  solution,  precipitates  of  double  salts  are  obtained,  con- 
taining varying  proportions  of  the  two  fluorides.  The  use  of 
aluminium  chloride  in  solution  would  dispense  with  the  objec- 
tion made  to  Deville's  analogous  method,  and  this  process 
would  very  probably  produce  cryolite  quite  cheaply. 

Brunerf  produced  aluminium  fluoride  by  passing  hydro- 
fluoric acid  gas  in  the  required  quantity  over  alumina  heated 
red  hot  in  a  platinum  crucible:  — 

Al20,  +  6HF=2A1F3  4  3H2O. 

Devillef  states  that  it  can  be  made  by  melting  together  the 
equivalent  quantities  of  cryolite  and  aluminium  sulphate : 

2(AlF3.3NaF)  -I-  Al,(S04)3.:eH,0  =  4AIF3  +  sNa^SO^  +  ;i;H.,0. 

On  washing  the  fusion,  sodium  sulphate  goes  into  the  solu- 
tion. It  is  also  stated  that  hydrochloric  acid  gas  acting  on  a 
mixture  of  fluorspar  and  alumina  at  a  high  temperature  will 
produce  aluminium  fluoride : 

AlA  +  sCaF^  +  6HC1  =  2AIF3  4-  aCaCl,  -1-  3H.,0. 

The  calcium  chloride  would  be  partly  volatilized  and  the  re- 
mainder washed  out  of  the  fusion. 

Hautefeuille§   obtained   crystallized    aluminium   fluoride  by 

♦German  Patent  (D.  R.  P.),  No.  35,212. 

t  Pogg-  Annalen,  98,  p.  488. 

t  Ann.  de.  Chim.  et  de  Phys.  [3],  61,  p.  333;  [3],  49,  p.  79. 

§Idem,  [4],  4.P-  iS3- 


passing  hydrofluoric  acid  gas  and  steam  together  over  red-hot 

Ludwig  Grabau,  of  Hanover,  bases  his  process  of  producing 
aluminium  on  the  reduction  of  aluminium  fluoride  (see  Chap. 
X.),  which  is  prepared  on  a  commercial  scale  by  the  following 
ingenious  methods : 

*  The  process  is  based  on  the  conversion  of  aluminium  sul- 
phate into  fluoride  by  reaction  with  cryolite,  the  fluoride  being 
afterward  reduced  by  sodium  in  such  a  manner  that  a  double 
fluoride  of  sodiuni  and  aluminium  results,  which  is  used  over 
again,  thus  forming  a  continuous  process.  The  purest  obtain- 
able cryolite  is  used  to  start  the  process,  after  which  no  more 
is  needed,  the  material  supplying  the  aluminium  being  its  sul- 
phate, which  can  be  obtained  cheaply  in  large  quantities,  and 
almost  perfectly  pure.  The  process  is  outlined  by  the  reac- 

2  (AlFa-sNaF)  +  AUCSO*),  =  4AIF3  +  sNa.SO^ 
2AIF3  +  sNa  =  AH  AlFs.sNaF. 

It  is  thus  seen  that  theoretically  the  cryolite  would  be  exactly 
reproduced,  but  the  losses  and  incomplete  reactions  unavoida- 
ble in  practice  would  cause  less  to  be  obtained,  and  necessitate 
the  continual  addition  of  fresh  cryolite ;  since,  however,  it  is 
not  desired  to  base  the  process  on  the  continual  use  of  cryo- 
lite, because  of  the  impurities  in  that  mineral,  an  indirect  pro- 
cess is  used,  consisting  of  two  reactions,  in  place  of  the  first 
given  above,  in  which  theoretically  a  larger  quantity  of  cryolite 
is  finally  obtained  than  is  used  to  begin  with.  This  is  operated 
by  introducing  fluorspar  into  the  process,  the  base  of  which 
goes  out  as  calcium  sulphate  or  gypsum,  and  so  supplies  the 
fluorine  needed. 

In  practice,  a  solution  of  aluminium  sulphate  is  heated  with 
powdered  fluorspar  (obtained  as  pure  as  possible  and  further 
cleaned    by  treatment  with    dilute    hydrochloric    acid).      The 

♦German  Patent  (D.  R.  P.),  No.  48,535.  March  8,  1889. 


aluminium  sulphate  will  not  be  entirely  converted  into  fluoride, 
as  has  been  previously  observed  by  Friedel,*  but  about  two- 
thirds  of  the  sulphuric  acid  is  replaced  by  fluorine,  forming  a 
fluorsulphate  of  aluminium.  This  latter  compound  remains  in 
solution,  while  gypsum  and  undecomposed  fluorspar  remain  as 
a  residue  and  are  filtered  out. 

AlaCSO,)^-!-  2CaF,  =  Al^F.CSOi)  +2  CaSOi. 

This  solution  is  concentrated  and  mixed  with  cryolite  in  such 
proportion  that  the  alkali  in  the  latter  is  just  equivalent  to  the 
sulphuric  acid  in  the  fluor-sulphate.  The  mass  is  dried  and 
gnited,  and  the  product  washed  and  dried. 

3AUF,(S0,)  +  2(AlF3.3NaF)  =8A1F3+  3Na,S04. 

On  reduction  with  sodium,  the  8  molecules  of  aluminium  fluor- 
ide, treated  with  sodium  as  by  the  reaction  given,  produce  4 
molecules  of  the  double  fluoride.  It  is  thus  seen  that  after 
allowing  for  reasonable  losses  in  the  process  there  is  much  . 
more  cryolite  produced  than  is  used,  and  the  excess  can  be 
very  profitably  sold  as  pure  cryolite,  being  absolutely  free  from 
iron  or  silica. 

Grabau  proposed  to  obtain  his  aluminium  sulphate  solution 
directly  from  kaolin,  by  treatment  with  sulphuric  acid,  and  thus 
utilize  this  most  abundant  of  the  aluminous  minerals.  It  is 
claimed  that  aluminium  fluoride  of  the  greatest  purity  can  be 
thus  manufactured  at  a  less  cost  than  pure  alumina  can  be 

More  recently  the  method  of  production  has  been  varied  as 
follows:!  To  produce  aluminium  fluoride  free  from  silicon  and 
iron,  calcined  clay  or  kaolin  is  stirred  in  excess  into  dilute  hy- 
drofluoric acid,  a  12  per  cent,  solution  of  which  is  recommended. 
The  violent  reaction  ensuing  is  moderated  by  cooling,  so  that 
the  temperature  does  not  exceed  95°.    After  a  few  minutes  the 

*  Bull,  de  la  Soc.  Chimique  [2],  xxi,  241. 

t  German  Patent  No.  69,791,  August  20,  1892. 


liquor  is  neutralized,  as  may  be  tested  by  a  drop  giving  a  pure 
yellow  with  tropaolin.  This  neutrality  is  essential  to  ensure 
the  solution  being  free  from  silica.  Further,  this  neutrality 
cannot  be  obtained  using  uncalcined  clay,  nor  with  clay  which 
has  been  too  highly  heated.  The  clay  must  be  calcined  at  a 
certain  determined  temperature,  which  can  only  be  learned  by 
experience.  The  hot,  neutral  solution  is  cooled  to  a  moderate 
temperature  and  filtered  quickly,  washing  the  residue  with  hot 
water.  On  an  average  the  equivalent  of  95  per  cent,  of  the  hy- 
drofluoric? acid  used  can  be  obtained  in  the  form  of  dissolved 
aluminium  fluoride.  The  solution  will  be  free  from  dissolved 
silica,  but  may  contain  iron,  lead,  arsenic  or  other  accidental 
impurities.  In  order  to  separate  out  pure  aluminium  fluoride 
from  this  solution,  Grabau  has  patented  the  following  method  of 
procedure  :*  The  solution  is  first  treated  with  sulphuretted  hy- 
drogen gas,  which  precipitates  any  lead,  copper,  arsenic,  etc., 
which  may  be  present,  and  reduces  any  ferric  salt  present  to  the 
ferrous  state.  Any  other  reducing  agent  could  also  be  used  to 
effect  this.  The  solution  is  filtered  and  slightly  acidified,  so 
that  a  test  drop  turns  red  with  tropaolin.  A  neutral  solution 
holding  hydrogen  sulphide  would  in  the  subsequent  cooHng  de- 
posit traces  of  iron  sulphide.  The  acidified  solution  is  then 
str-ongly  cooled  in  a  receptacle,  which  may  be  of  sheet  alumin- 
ium. There  at  once  separates  out  crystalline,  hydrated  alu- 
minium fluoride,  AIF3.9H2O.  It  is  best  to  start  the  crystalliza- 
tion by  dropping  in  a  trace  of  the  crystallized  salt.  As  soon  as 
the  crystallization  commences  the  temperature  rises ;  when  it 
again  sinks  to  0°  by  continuing  the  cooling,  the  crystallization 
is  ended.  The  thick  crystal  liquor  is  separated  on  filters  or  in 
a  centrifugal  machine,  into  mother  liquor  and  crystals;  the 
latter  are  washed  with  ice-cold  water.  These  crystals  are  free 
from  iron,  but  if  the  solution  had  not  been  previously  reduced, 
noticeable  quantities  of  ferric  fluoride  would  have  been  in  them. 
These  crystals  are  easily  dried  and  the  water  driven  off  by 
gentle  heating. 

♦German  Patent  No.  70,155,  August  20,  1892. 

1 7  i  ALUMINIUM. 


The  Preparation  of  Aluminium  Sulphide. 

Until  the  researches  of  M.  Fremy,  no  other  method  of  pro- 
ducing aluminium  sulphide  was  known  save  by  acting  on  the 
metal  with  sulphur  at  a  very  high  heat.  Fremy  was  the  first 
to  open  up  a  diflferent  method,  and  it  may  be  that  his  discov- 
eries will  yet  be  the  basis  of  successful  industrial  processes.  In 
order  to  understand  just  how  much  he  discovered,  w?  here  give 
all  that  his  original  paper  contains   concerning  this  sulphide.* 

"We  know  that  sulphur  has  no  action  on  silica  or  boric  ox- 
ide, magnesia,  or  alumina.  I  thought  that  it  might  be  possible 
to  replace  the  oxygen  by  sulphur  if  I  introduced  or  intervened 
a  second  affinity,  as  that  of  carbon  for  oxygen.  These  decom- 
positions produced  by  two  affinities  are  very  frequent  in  chem- 
istry ;  it  is  thus  that  carbon  and  chlorine,  by  acting  simultane- 
ously on  silica  or  alumina,  produce  silicon  or  aluminium 
chloride,  while  either  alone  could  not  decompose  it ;  a  similar 
case  is  the  decomposition  of  chromic  oxide  by  carbon  bisul- 
phide, producing  chromium  sesquisulphide.  Reflecting  on 
these  relations,  I  thought  that  carbon  bisulphide  ought  to  act 
at  a  high  heat  on  silica,  magnesia,  and  alumina,  producing 
easily  their  sulphides.  Experiment  has  confirmed  this  view. 
I  have  been  able  to  obtain  in  this  way  almost  all  the  sulphides 
which  until  then  had  been  produced  only  by  the  action  of  sul- 
phur on  the  metals. 

"  To  facilitate  the  reaction  and  to  protect  the  sulphide  from 
the  decomposing  action  of  the  alkalies  contained  in  the  por- 
celain tube  which  was  used,  I  found  it  sometimes  useful  to  mix 
the  oxides  with  carbon  and  to  form  the  mixture  into  bullets 
resembling  those  employed  in  the  preparation  of  aluminium 
chloride.  I  ordinarily  placed  the  bullets  in  little  carbon  boats, 
and  heated  the  tube  to  whiteness  in  the  current  of  vaporized 

*  Ann.  de  Chim.  et  de  Phys.  [3],  38,  p.  312. 


carbon  bisulphide.     The  presence  of  divided  carbon  does  not 
appear  useful  in  the  preparation  of  this  sulphide. 

"  The  aluminium  sulphide  formed  is  not  volatile  ;  it  remains 
in  the  carbon  boats  and  presents  the  appearance  of  a  melted 
vitreous  mass.  On  contact  with  water  it  is  immediately  de- 
composed : 

A1,S,  +  3H,0  =  Al,03  +  3H,S. 

"  The  alumina  is  precipitated,  no  part  of  it  going  into  solu- 
tion. This  precipitated  alumina  is  immediately  soluble  in  weak 
acids.  The  clear  solution,  evaporated  to  dryness,  gives  no 
trace  of  alumina.  It  is  on  this  phenomenon  that  I  base  the 
method  of  analysis. 

"  Aluminium  sulphide  being  non-volatile,  it  is  always  mixed 
with  some  undecomposed  alumina.  It  is,  in  fact,  impossible  to 
entirely  transform  all  the  alumina  into  sulphide.  I  have  heated 
less  than  a  gramme  of  alumina  to  redness  five  or  six  hours  in 
carbon  bisulphide  vapor,  and  the  product  was  always  a  mixture 
of  alumina  and  aluminium  sulphide.  The  reason  is  that  the 
sulphide,  being  non-volatile  and  fusible,  coats  over  the  alumina 
and  prevents  its  further  decomposition.  The  alumina  thus 
mixed  with  the  sulphide,  and  which  has  been  exposed  to  a  red 
heat  for  a  long  time,  is  very  hard,  scratches  glass,  and  is  in 
grains  which  are  entirely  insoluble  in  acids.  By  reason  of  this 
property  I  have  been  able  to  analyze  the  product  exactly,  for 
on  treating  the  product  with  water  and  determining  on  the  one 
hand  the  sulphuretted  hydrogen  evolved,  and  on  the  other  the 
quantity  of  soluble  alumina  resulting,  I  have  determined  the 
two  elements  of  the  compound.  One  gramme  of  my  product 
contained  0.365  grm.  of  aluminium  sulphide,  or  36.5  per  cent., 
the  remainder  being  undecomposed  alumina." 

The  composition  of  this  sulphide  was— 

Aluminium °-i37  g™-  =  37-5  pef  cent. 

Sulphur 0.228     "=62.5 

0.365      "       lOO.O  " 


The  formula  AI2S3  requires — 

Aluminium 36.3  per  cent. 

Sulphur 63.7         " 

The  above  is  the  substance  of  Fremy's  investigations  and 
results.  Reichel*  next  published  an  account  of  further  experi- 
ments in  this  line.  He  found  that  by  melting  alumina  and  sul- 
phur together  no  reaction  ensued.  In  the  case  of  magnesia,  the 
sulphide  was  formed  if  carbon  was  mixed  with  the  magnesia 
and  sulphur,  but  this  change  did  not  alter  the  alumina.  Hydro- 
gen gas  passed  over  a  mixture  of  alumina  and  sulphur  likewise 
gave  negative  results.  Sulphuretted  hydrogen  passed  over  ig- 
nited alumina  did  not  succeed.  By  filling  a  tube  with  pure  alu- 
mina, passing  in  hydrogen  gas  and  the  vapor  of  carbon  bisul- 
phide, the  heating  being  continued  until  carbon  bisulphide 
condensed  in  the  outlet  tube,  and  then  hydrogen  being  passed 
through  until  the  tube  was  cold,  a  product  was  obtained  con- 
taining aluminium  sulphide  and  undecomposed  alumina. 

In  1886,  the  writer  made  a  series  of  experiments  on  the  pro- 
duction and  reduction  of  aluminium  sulphide.  Alumina,  either 
alone  or  mixed  with  carbon  or  with  carbon  and  sulphur,  was 
put  in  porcelain  or  carbon  boats  into  a  hard  glass  or  porcelain 
tube.  This  was  then  heated  and  vapor  of  carbon  bisulphide 
passed  through  it.  The  product  was  analyzed  according  to 
Fremy's  directions.  The  proportion  of  aluminium  sulphide 
obtained  in  the  product  varied  from  13  to  40  per  cent.  The 
best  result  was  obtained  at  the  highest  heat — almost  whiteness. 
The  presence  of  sulphur  or  carbon,  or  both  together,  mixed 
with  the  alumina,  did  not  promote  to  any  degree  the  formation 
of  a  richer  product.  The  conditions  for  obtaining  the  best  re- 
sults seem  to  be  high  heat  and  fine  division  of  the  alumina  to 
facilitate  its  contact  with  the  carbon  bisulphide  vapor.  The 
product  was  light-yellow  when  not  mixed  with  carbon,  easily 
pulverized,  and  evolved  sulphuretted  hydrogen  gas  energetically 

*  Jahresb.  der  Chemie,  1867,  p.  155. 


when  dropped  into  water.  Since  carbon  bisulphide  can  now  be 
manfactured  at  a  very  low  price,  say  2  to  3  cents  per  lb.,  it  is 
not  impossible  that  it  may  be  found  profitable  to  produce 
aluminium  from  its  sulphide.  In  such  a  case,  large  retorts 
would  be  used,  a  stirring  apparatus  would  facilitate  the  forma- 
tion of  a  richer  product,  and  the  unused  carbon  bisulphide 
could  be  condensed  and  saved. 

M.  Comenge,*  of  Paris,  proposed  to  prepare  aluminium  sul- 
phide by  using  a  clay  retort  similar  to  those  used  in  gas-works, 
filling  it  one- half  its  length  with  charcoal  or  coke  and  the  other 
half  with  alumina.  The  retort  being  heated  to  rednesss,  sul- 
phur is  introduced  at  the  coke  end,  when  in  contact  with  the 
carbon  it  forms  carbon  bisulphide,  which  acts  upon  the  alumina 
at  the  other  end,  producing  the  sulphide. 

Messrs.  Reillon,  Montague,  and  Bourgerel  f  obtained  a  pat- 
ent in  England  for  producing  aluminium,  in  which  aluminium 
sulphide  is  obtained  by  mixing  powdered  alumina  with  40 
per  cent,  of  its  weight  of  charcoal  or  lampblack  and  formed 
into  a  paste  with  a  sufficient  quantity  of  oil  and  tar.  This  is 
then  calcined  in  a  closed  vessel  and  an  aluminous  coke  ob- 
tained. This  is  broken  into  pieces,  put  into  a  retort,  and 
treated  with  carbon  bisulphide  vapor.  The  inventors  state 
that  the  reaction  takes  place  according  to  the  formula 

2 A1,0,  +  3C  +  3CS,  =  4A1,S,  -^  6C0. 

PetitjeanI  states  that  if  alumina  is  mixed  with  tar  or  turpentine 
and  ignited  in  a  carbon-lined  crucible,  and  the  coke  obtained 
mixed  intimately  with  sulphur  and  carbonate  of  soda  and  ig- 
nited a  long  time  at  bright  redness,  there  results  a  double  sul- 
phide of  aluminium  and  sodium,  from  which  aluminium  can  be 
easily  extracted. 

It  has  been  stated  §   that  if  aluminium  fluoride  is  heated  with 

*  English  Patent,  1858,  No.  461. 
t  English  Patent,  No.  4,756,  March  28,  1887. 
JPolytechnisches  Central.  Blatt.,  1858,  p.  888. 
§  Chemical  News,  i860. 


calcium  sulphide,  aluminium  sulphide  results.  F.  Lauterborn* 
also  makes  the  same  claim  in  a  patent  twenty  years  later,  but 
the  possibility  of  this  reaction  taking  place  is  not  yet  beyond 

*  German  Patent  (D.  R.  P.),  No.  14,495  (1880). 



Some  years  ago,  in  order  to  treat  fully  of  the  metallurgy  of 
aluminium  it  would  have  been  as  necessary  to  accompany  it 
with  all  the  details  of  the  manufacture  of  sodium  as  to  give  the 
details  of  the  reduction  of  the  aluminium,  because  the  manu- 
facture of  the,  former  was  carried  on  solely  in  connection  with 
that  of  the  latter.  But  now  sodium  has  come  out  of  the  list  of 
chemical  curiosities,  and  has  become  an  article  of  commerce, 
used  for  many  other  purposes  than  the  reduction  of  aluminium. 
In  fact,  the  last  four  years  has  seen  the  almost  total  extinction 
of  the  sodium  processes  of  producing  aluminium.  If  it  be  asked 
why  such  a  chapter  as  this  is  still  retained  in  a  treatise  on  alu- 
minium, the  answer  is  that  for  thirty  years  aluminium  was 
made  solely  by  its  use;  sodium  is  bound  up  with  the  history  of 
aluminium ;  and  it  is  not  impossible,  though  perhaps  improba- 
ble, that  some  improved  form  of  sodium  process,  in  which  me- 
tallic sodium  is  produced  and  at  once  utilized  in  the  one  ope- 
ration, may  yet  find  a  footing  in  the  aluminium  industry.  For 
these  and  other  reasons  which  might  be  advanced,  the  methods 
of  producing  sodium  are  yet  of  considerable  interest  to  the 
worker  in  aluminium,  and  are  therefore  retained,  with  the  addi- 
tion of  a  few  recent  processes. 

Davy  to  Deville  (1808-1855). 

Sodium  was  first  isolated  by  Davy  by  the  use  of  electricity  in 

the  year  1808.*     Later,  Gay  Lussac  and  Thenard  made  it  by 

decomposing  at  a  very  high  temperature  a  mixture  of  sodium 

carbonate  and  iron    filings,  f       In    1808,  also,  Curaudau    an- 

*  Phil.  Trans.,  :8o8. 
fRecherches  Physico-chimiques,  1810. 



nounced  that  he  had  succeeded  in  producing  potassium  or 
sodium  without  using  iron,  simply  by  decomposing  their  car- 
bonates by  means  of  animal  charcoal.  Briinner,  continuing 
this  investigation,  used  instead  of  animal  charcoal  the  so-called 
black  flux,  the  product  obtained  by  calcining  crude  tartar  from 
wine  barrels.  He  was  the  first  to  use  the  wrought-iron  mer- 
cury bottles.  The  mixture  was  heated  white  hot  in  a  furnace, 
the  sodium  volatilized,  and  was  condensed  in  an  iron  tube 
screwed  into  the  top  of  the  flask,  which  projected  from  the  fur- 
nace and  was  cooled  with  water.  In  Brunner's  experiments  he 
only  obtained  three  per  cent,  of  the  weight  of  the  mixture  as 
metallic  sodium,  the  rest  of  the  metal  being  lost  as  vapor. 
Donny  and  Mareska  gave  the  condenser  the  form  which  with 
a  few  modifications  it  retains  to-day. 
It  was  of  iron,  4  millimetres  thick,  and 
was  made  in  the  shape  of  a  book, 
having  a  length  of  about  100  centi- 
metres, breadth  50,  and  depth  6  (see 
Fig.  9).  This  form  is  now  so  well 
known  that  a  further  description  is 
unnecessary.  With  this  condenser  the 
greatest  difficulty  of  the  process  was 
removed,  and  the  operation  could  be 
carried  on  in  safety.  This  apparatus 
was  devised  and  used  by  Donny  and  Mareska  in  1854,  with  the 
supervision  of  Deville. 

FlQ.  9. 

Deville' s  Improvements  at  Javel  (1855). 

The  following  is  Deville's  own  description  of  the  attempts 
which  he  made  to  reduce  the  cost  of  producing  sodium.  As 
far  as  we  can  learn  these  experiments  were  commenced  in  1854, 
but  the  processes  about  to  be  given  are  those  which  were  car- 
ried out  at  Javel,  March  to  June,  1855.  As  the  description 
contains  so  many  allusions  to  the  difficulties  met  not  only  in  pro- 
ducing but  also  in  handling  and  preserving  sodium,  its  perusal 
is  yet  of  value  to  all  concerned  in  this  subject,  although  the 


actual  methods  here  described  have  been  superseded  by  much 
more  economical  ones. 

Properties  of  sodium. — "The  small  equivalent  of  sodium  and 
the  low  price  of  sodium  carbonate  should  long  since  have 
caused  it  to  be  preferred  to  potassium  in  chemical  operations, 
but  a  false  idea  prevailed  for  a  long  time  concerning  the  diffi- 
culties accompanying  the  reduction.  When  I  commenced 
these  researches  the  cost  of  sodium  was  at  least  double  that  of 
potassium.  In  this  connection  I  can  quote  from  my  memoir 
published  in  the  Ann.  de  Chim.  et  de  Phys.,  Jan.,  i,  1855  :  "I 
have  studied  with  care  the  preparation  of  sodium  and  its  prop- 
erties with  respect  to  oxygen  and  the  air,  in  order  to  solve  the 
difficulties  which  accompany  its  reduction  and  the  dangers  of 
handling  it.  In  this  later  respect,  sodium  is  not  to  be  com- 
pared to  potassium.  As  an  example  of  how  dangerous  the 
latter  is,  I  will  relate  that  being  used  to  handle  sodium  and 
wishing  once  to  replace  it  with  potassium,  the  simple  rubbing 
of  the  metal  between  two  sheets  of  paper  sufficed  to  ignite  it 
with  an  explosion.  Sodium  may  be  beaten  out  between  two 
sheets  of  paper,  cut  and  handled  in  the  air,  without  accident  if 
the  fingers  and  tools  used  are  not  wet.  It  may  be  heated  with 
impunity  in  the  air,  even  to  its  fusing  point,  without  taking  fire, 
and  when  melted,  oxidation  takes  place  slowly,  and  only  at  the 
expense  of  the  moisture  of  the  air.  I  have  even  concluded 
that  the  vapor  alone  of  sodium  is  inflammable,  but  the  vivid 
combustion  of  the  metal  can  yet  take  place  at  a  temperature 
which  is  far  below  its  boiling  point,  but  at  which  the  tension  of 
the  metallic  vapors  has  become  sensible."  I  will  add  to  these 
remarks  that  sodium  possesses  two  considerable  advantages : 
it  is  obtained  pure  at  the  first  operation,  and,  thanks  to  a 
knack  which  I  was  a  long  time  in  finding  out,  the  globules  of 
the  metal  may  be  reunited  and  treated  as  an  ordinary  metal 
when  melting  and  casting  in  the  air.  I  have  thus  been  able  to 
dispense  with  the  distillation  of  the  raw  products  in  the  manu- 
facture— an  operation  which  had  come  to  be  behaved  neces- 
sary, and  which   occasioned  a  loss  of  50  per  cent,  or  so  on  the 


return,  without  appreciable  advantage  to  the  purity  of  the 
metal.  The  manufacture  of  sodium  is  in  no  manner  encum- 
bered by  the  carburetted  products,  or  perhaps  nitrides,  which 
are  very  explosive,  and  render  the  preparation  of  potassium  so 
dangerous.  I  ought  to  say,  however,  that  by  making  potas- 
sium on  a  large  scale  by  the  processes  I  am  about  to  describe 
for  sodium,  Rousseau  Bros,  have  diminished  the  dangers  of  its 
preparation  very  much,  and  practice  the  process  daily  in  their 
chemical  works. 

Method  employed.  The  method  of  manufacture  is  founded 
on  the  reaction  of  carbon  on  alkaline  carbonate.  This  method 
has  been  very  rarely  applied  to  sodium,  but  is  used  every  day 
for  producing  potassium.  Brunner's  process  is,  in  fact,  very 
difficult  to  apply,  great  trouble  being  met,  especially  in  the 
shape  of  condenser  used.  It  is  Donny  and  Mareska  who  have 
mastered  the  principles  which  should  guide  in  constructing 
these  condensers. 

Composition  of  mixtures  used.  The  mixture  which  has  given 
me  excellent  results  in  the  laboratory  is : 

Sodium  carbonate 717  parts. 

Wood  charcoal 1 75      " 

Chalk 108     " 


Dry  carbonate  of  soda  is  used,  the  carbon  and  chalk  pulver- 
ized, the  whole  made  into  a  paste  with  oil  and  calcined  in  a 
crucible.  The  end  of  a  mercury  bottle,  cut  off,  serves  very 
well,  and  can  be  conveniently  closed.  Oil  may  be  used  alto- 
gether in  place  of  charcoal,  in  which  case  the  following  pro- 
portions are  used : 

Sodium  carbonate 625  parts. 

Oil 280      " 

Chalk 95      " 

That  a  mixture  be  considered  good,  it  should  not  melt  at  the 
temperature  at  which  sodium  is  evolved,  becoming  liquid  at 


this  point  and  so  obstructing  the  disengagement  of  the  gas.* 
But  it  should  become  pasty,  so  as  to  mold  itself  evenly  against 
the  lower  side  of  the  iron  vessel  in  which  it  is  heated.  The 
considerable  latent  heat  required  by  carbonic  oxide  and  sodium 
in  assuming  the  gaseous  state,  is  one  cause  of  cooling  which  re- 
tards the  combustion  of  the  iron.  When  soda  salt  is  intro- 
duced in  place  of  dried  soda  crystals,  the  mixture,  whatever  its 
composition,  always  melts,  the  gases  making  a  sort  of  ebulli- 
tion, the  workmen  saying  that  the  apparatus  "  sputters."  This 
behavior  characterizes  a  bad  mixture.  It  has  been  demon- 
strated to  me  that  the  economy  made  at  the  expense  of  a 
material  such  as  carbonate  of  soda,  the  price  of  which  varies 
with  its  strength  in  degrees,  and  which  forms  relatively  a  small 
portion  of  the  cost  of  sodium,  is  annulled  by  a  decrease  of  20  to 
25  per  cent,  in  the  return  of  sodium.  The  oil  used  ought  to  be 
dry  and  of  long  flame.  It  acts  as  a  reducing  agent,  and  also 
furnishes  during  the  whole  operation  hydrogenous  gases,  and 
even,  towards  the  close,  pure  hydrogen,  which  help  to  carry 
the  sodium  vapor  rapidly  away  into  the  condenser,  and  to 
protect  the  condensed  metal  from  the  destructive  action  of  the 
carbonic  oxide.  Oil  renders  a  similar  service  in  the  manu- 
facture of  zinc.  The  role  of  the  chalk  is  easy  to  understand. 
By  its  infusibility  it  decreases  the  liability  of  the  mixture  to 
melt.  Further  it  gives  off  carbonic  acid,  immediately  reduced 
by  the  carbon  present  to  carbonic  oxide.  Now,  the  sodium 
ought  to  be  carried  rapidly  away  out  of  the  apparatus,  because 
it  has  the  property  of  decomposing  carbonic  oxide,  which  is 
simultaneously  formed,  within  certain  limits  of  temperature, 
especially  if  the  sodium  is  disseminated  in  little  globules  and 
so  presents  a  large  surface  to  the  destructive  action  of  the  gas. 
It  is  necessary,  then,  that  the  metallic  vapors  should  be  rapidly 
conducted  into  the  condenser  and  brought  into  the  liquid  state 

*  It  seems  plain,  however,  granting  that  vapors  would  be  evolved  most  freely  from 
2.  perfectly  infusible  charge,  that  a  pasty  condition,  such  as  is  recommended  in  the 
next  sentence,  would  be  the  worst  possible  state  of  the  charge  for  evolving  gas,  being 
manifestly  inferior  to  a  completely  fluid  bath.— J.  W.  R. 


— not  into  that  state  comparable  to  "flowers  of  sulphur,"  in 
which  the  metal  is  very  oxidizable  because  of  its  fine  division. 
A  rapid  current  of  gas,  even  of  carbonic  oxide,  actively  carries 
the  vapors  into  the  condenser,  which  they  keep  warm  and  so 
facilitate  the  reunion  of  the  globules  of  sodium.  At  La 
Glaciere  and  Nanterre  a  mixture  was  used  in  which  the,  pro- 
portion of  chalk,  far  from  being  diminished,  was,  on  the  con- 
trary, increased.     The  proportions  used  were — 

Sodium  carbonate 40  kilos  =  597  parts. 

Oil 18     "     =269      " 

Chalk 9     "     =134      " 

67  1000 

This  quantity  of  mixture  ought  to  give  9.4  kilos  of  sodium, 
melted  and  cast  into  ingots,  without  counting  the  metal  divided 
and  mixed  with  foreign  materials,  of  which  a  good  deal  is 
formed.  This  return  would  be  one-seventh  of  the  weight  of 
the  mixture,  or  one-quarter  of  the  sodium  carbonate  used. 

Use  of  these  mixtures.  The  carbonate  of  soda,  charcoal,  and 
chalk  ought  to  be  pulverized  and  sieved,  well  mixed  and  again 
sieved,  in  order  to  make  a  very  intimate  mixture ;  the  mixture 
ought  to  be  used  as  soon  as  possible  after  preparing,  that  it 
may  not  take  up  moisture.  The  mixture  may  be  put  just  as  it 
is  into  the  apparatus  where  it  should  furnish  sodium,  but  it  may 
very  advantageously  be  previously  calcined  so  as  to  reduce  its 
volume  considerably,  and  so  permit  a  greater  weight  being  put 
into  the  same  vessel.  I  believe  that  whenever  this  calcination 
may  be  made  with  economy,  as  with  the  waste  heat  of  a  fur- 
nace, a  gain  is  made  by  doing  so,  but  the  procedure  is  not  in- 
dispensable. However,  the  utility  of  it  may  be  judged  when 
it  is  stated  that  a  mercury  bottle  held  two  kilos  of  non-calcined 
mixture,  but  3.6  kilos  were  put  into  one  when  previously  cal- 
cined. These  two  bottles  heated  in  the  same  fire  for  the  same 
time  gave  quantities  of  sodium  very  nearly  proportional  to  the 
weight  of  soda  in  them.  In  working  under  the  direction  of  a 
good   workman,  who   made  the  bottles  serve   for  almost  four 


operations,  I  have  been  able  to  obtain  very  fine  sodium  at  as 
low  a  price  as  9.25  francs  per  kilo.  ($0.84  per  pound).  In  the 
manufacture  of  sodium  by  the  continuous  process,  where  the 
materials  may  be  introduced  red  hot  into  the  apparatus,  this 
preliminary  calcination  is  a  very  economical  operation. 

Apparatus  for  reducing,  condensing,  and  heating. — M.  Briin- 
ner  had  the  happy  idea  of  employing  mercury  bottles  in  manu- 
facturing potassium  ;  thus  the  apparatus  for  reduction  was  in  the 
hands  of  any  chemist,  and  at  such  a  low  price  that  any  one  has 
been  able  to  make  potassium  without  much  trouble.  These 
bottles  are  equally  suitable  for  preparing  sodium,  and  the 
quantity  which  may  be  obtained  from  such  apparatus  and  the 
ease  with  which  they  are  heated,  are  such  that  they  might  have 
been  used  a  long  time  for  the  industrial  manufacture,  except 
for  two  reasons  which  tend  to  increase  the  price  of  these  bottles 
continually.  For  some  time  a  large  number  of  bottles  have 
been  sent  to  the  gold  workers  of  Australia  and  California,  also 
large  quantities  have  been  used  in  late  years  in  preparing  the 
alkaline  metals ;  these  two  facts  have  diminished  the  number  to 
such  a  point  that  from  0.5  or  i  franc  the  price  has  been  raised 
to  2.5  or  3  francs.  It  has  thus  become  necessary  to  replace 
them,  which  has  been  done  by  substituting  large  wrought-iron 
tubes  which  have  the  added  advantage  of  being  able  to  be 
worked  continuously.  I  will  first  describe  the  manufacture  in 
mercury  bottles,  which  may  still  be  very  advantageously  used 
in  the  laboratory,  and  afterwards  the  continuous  production  in 
large  iron  cylinders  as  now  worked  industrially. 

Manufacture  in  mercury  bottles. — The  apparatus  needed  is 
composed  of  a  furnace,  a  mercury  bottle,  and  a  condenser. 

The  form  of  furnace  most  suitable  is  a  square  shaft,  C  (Fig. 
10),  the  sides  of  which  are  refractory  brick,  while  the  grate  G 
ought  to  have  movable  grate  bars,  the  furnace  being  connected 
above  with  a  chimney  furnishing  good  draft.  The  flue  F,  con- 
necting with  the  chimney,  should  have  a  damper,  R,  closing 
tightly,  and  should  lead  exactly  from,  the  centre  of,  the  top  of 
the  shaft,  thus  dividing  the  draft  equally  all  over  the    grate. 

1 86 


Coke  is  charged  through  lateral  openings  at  0.  A  small  open- 
ing closed  by  a  brick  should  be  left  a  short  distance  above  the 
grate  bars,  in  order  to  poke  down  the  coke  around  the  bottle 
should  it  not  fall  freely.  The  space  between  the  grate  and 
bottle  should  always  be  full  of  fuel  in  order  to  keep  the  iron  of 
the  bottle  from  being  burnt.  In  front  of. the  furnace  is  a  square 
opening,  P,  closed  with  an  iron  plate,  which  has  a  hole  in  it  by 
which  the  tube  T  issues  from  the  furnace. 

The  mercury  bottle  is  supported  on  two  refractory  bricks, 
KK,  cut  on  their  top  side  to  the  curve  of  the  bottle.     These 

Fig.  10. 

should  be  at  least  20  centimetres  high  to  maintain  between  the 
grate  and  the  bottle  a  convenient  distance.  The  illustration 
gives  the  vertical  dimensions  correctly,  but  the  horizontal 
dimensions  are  somewhat  shortened.  There  should  be  at  least 
12  centimetres  between  the  bottle  and  sides  of  the  furnace. 
However,  all  these  dimensions  should  vary  with  the  strength  of 
the  chimney  draft  and  the  kind  of  fuel  used ;  the  furnace 
should  be  narrower  if  the  draft  is  very  strong  and  the  coke 
dense.  The  iron  tube  T,  which  may  conveniently  be  made  of 
a  gun  barrel,  is  either  screwed  into  the  bottle  or  it  may  be 
simply  fitted  and   forced  into  place,  provided  it  hold  tightly 


enough.  It  should  be  about  5  to  6  centimetres  long,  and 
should  project  scarcely  i  centimetre  from  the  furnace.  The 
end  projecting  should  be  tapered  off  in  order  to  fit  closely  into 
the  neck  of  the  condenser. 

The  condenser  is  constructed  with  very  little  deviation  from 
that  given  by  Donny  and  Mareska  (see  Fig.  9,  p.  180).  I 
have  tried  my  best  to  make  this  apparatus  as  perfect  as 
possible,  but  have  always  reverted  to  the  form  described  by 
those  authors ;  yet  even  the  very  small  differences  I  have  made 
are  indispensable  and  must  be  rigidly  adhered  to  if  it  is  wished 
to  get  the  best  results  obtainable.  Two  plates  of  sheet  iron,  2 
to  3  millimetres  thick,  are  taken  and  cut  into  the  shape  indi- 
cated by  Fig.  II.  One  plate.  A,  remains  flat  except  at  the 
point  C,  where  it  is  drawn  by  hammering  into  a  semi- 
cylindrical  neck  of  about  25  millimetres  inside  diameter.     This 

Fig.  II. 

iiiiii  111! 

■corresponds  with  a  similar  neck  in  the  other  plate,  so  that  on 
joining  the  two  there  is  a  short  cylinder  formed.  The  edges  of 
the  plate  A  are  raised  all  around  the  sides  about  5  to  6  milli- 
metres, so  that  when  the  two  plates  are  put  together  the  longi- 
tudinal section  from  £>  to  Cis  as  in  Fig.  12.  As  to  the  end, 
in  one  form  the  edge  was  not  turned  up,  leaving  the  end  open 
as  in  Fig.  13.  Another  form,  which  I  use  when  wishing  to  let 
the  sodium  accumulate  in  the  condenser  till  it  is  quite  full,  is 
made  by  turning  up  the  edge  at  the  end  all  but  a  small  space 
left  free,  thus  giving  the  end  the  appearance  of  Fig.  14,  this 
-device  also  being  shown  in  Fig.  11.     The  gas  evolved  during 


the  reaction  then  escapes  at  the  hole  0.  The  most  rational 
arrangement  of  the  apparatus  is  that  shown  in  Fig.  15.  In  this 
condenser  the  lower  part,  instead  of  being  horizontal,  is  in- 
clined, and  the  end  having  two  openings,  O  and  0' ,  the  sodium 
trickles  out  at  the  lower  one  as  it  condenses,  while  the  gas  es- 
capes by  the  slightly  larger  upper  opening.  In  placing  the 
plates  together,  the  raised  edges  are  washed  with  hme  so  as  to 
form  a  good  joint  with  the  flat  plate,  and  the  plates  are  kept 
together  by  strong  pressure  grips. 

To  conduct  the  operation,  the  bottles  are  filled  entirely  with 
mixture,  the  tube  T  adjusted,  and  then  placed  on  the  two  sup- 
ports, there  being  already  a  good  bed  of  fire  on  the  grate.  The 
front  is  put  up,  the  shaft  filled  with  coke,  and  the  damper 
opened.  The  gases  disengaged  from  the  bottle  are  abundant, 
of  a  yellow  color ;  at  the  end  of  half  an  hour  white  fumes  of 
carbonate  of  soda  appear.  The  condenser  should  not  yet  be 
attached,  but  it  should  be  noted  if  any  sodium  condenses  on  a 
cold  iron  rod  pushed  into  the  tube,  which  would  be  indicated 
by  its  fuming  in  the  air.  As  soon  as  this  test  shows  that  sodium 
is  being  produced,  the  condenser  is  attached  and  the  fire  kept 
quite  hot.  The  condenser  soon  becomes  warm  from  the  gases 
passing  through  it,  while  the  sodium  condenses  and  flows  out 
at  the  end  D  (Fig.  15).  It  is  received  in  a  cast-iron  basin  L, 
in  which  some  non-volatile  petroleum  is  put.  When  at  the  end 
of  a  certain  time  the  condenser  becomes  choked,  it  is  replaced 
by  another  which  has  been  previously  warmed  up  to  200°  or 
300°  by  placing  it  on  top  of  the  furnace.  If  the  closed  con- 
denser is  used,  care  must  be  taken  to  watch  when  it  becomes 
full,  on  the  point  of  running  from  the  upper  opening,  and  the 
condenser  then  replaced  and  plunged  into  a  cast-iron  pot  full 
of  petroleum  at  a  temperature  of  150°.  The  sodium  here 
melts  at  the  bottom  of  this  pot  and  is  ladled  out  at  the  end  of 
the  day.  The  oil  is  generally  kept  up  to  150°  by  the  hot  con- 
densers being  plunged  in  constantly.  The  pot  ought  to  have 
a  close  cover,  to  close  it  in  case  the  oil  takes  fire ;  the  extinc- 
tion of  the  fire  can  thus  be  assured  and  no  danger  results.     If 


the  oil  fires  just  as  a  condenser  is  being  introduced,  the  sodium 
is  run  out  in  the  air  without  igniting,  the  only  drawback  being 
that  the  condenser  must  be  cleaned  before  using  again.  This 
method  occasions  a  large  loss  of  oil,  however,  and  has  been 
completely  abandoned  for  the  other  form  of  condensers.  When 
the  operation  proceeds  well  only  pure  sodium  is  obtained,  the 
carbonized  products  which  accompany  in  so  provoking  a  man- 
ner the  preparation  of  potassium  not  occurring  in  quantity 
sufficient  to  cause  any  trouble.  Before  using  a  condenser  a 
second  time  it  is  put  on  a  grating  over  a  basin  of  petroleum 
and  rubbed  with  a  chisel-pointed  tool  in  order  to  remove  any 
such  carbonized  products.  From  time  to  time  this  material  is 
■collected,  put  into  a  mercury  bottle,  and  heated  gently.  The 
oil  first  distils,  and  is  condensed  in  another  cold  bottle.  The 
fire  is  then  urged,  a  condenser  attached,  and  the  operation  pro- 
ceeds as  with  a  fresh  charge,  much  sodium  being  thus  recov- 

The  raw  sodium  is  obtained  from  the  bottles  in  quantities 
of  over  half  a  kilo ;  it  is  perfectly  pure,  dissolving  in  absolute 
alcohol  without  residue.  It  is  melted  and  moulded  into  ingots 
just  as  lead  or  zinc.  The  operation  I  have  described  is  exe- 
cuted daily,  and  only  once  has  the  sodium  ignited.  To  prevent 
such  accidents  it  is  simply  necessary  to  keep  water  away  from 
the  apparatus.  The  reduction  of  carbonate  of  soda  and  the 
production  of  sodium  are  such  easy  operations  that  when  tried 
by  those  conversant  with  the  manufacture  of  potassium  or  who 
have  read  about  the  difficulties  of  the  production  of  sodium, 
success  is  only  gained  after  several  attempts — the  failure  being 
due  solely  to  excess  of  precautions.  The  reduction  should  be 
carried  on  rapidly,  so  that  a  bottle  charged  with  two  kilos  of 
rriixture  may  be  heated  and  emptied  in,  at  most,  two  hours.  It 
is  unnecessary  to  prolong  the  operation  after  the  yellow  flame 
stops  issuing  from  the  condenser,  for  no  more  sodium  is  ob- 
tained and  the  bottle  may  frequently  be  destroyed.  The 
temperature  necessary  for  the  reduction  is  not  so  high  as  it  has 
teen  so  far  iiriagined.     M.  Rivot,  who  has  assisted  in  these  ex- 


periments,  thinks  that  the  bottles  are  not  heated  higher  than 
the  retorts  in  the  middle  of  the  zinc  furnaces  at  Vielle  Mon- 
tagne.  I  have  been  even  induced  to  try  cast-iron  bottles,  but 
they  did  not  resist  the  first  heating,  without  doubt  because  they 
were  not  protected  from  the  fire  by  any  luting  or  covering.  But 
I  was  immediately  successful  in  using  cast-iron  bottles  decar- 
burized  by  the  process  used  for  making  malleable  castings. 
The  mercury  bottles  heated  without  an  envelope  ought  to  serve 
three  or  four  operations  when  entrusted  to  a  careful  workman. 
Besides  all  these  precautions,  success  in  this  work  depends 
particularly  on  the  ability  and  experience  of  the  workman,  who 
can  at  any  time  double  the  cost  of  the  sodium  by  carelessness 
in  managing  the  fire.  _ 

Continuous  manufacture  in  cylinders.  It  might  be  thought 
that  by  increasing  proportionately  in  all  their  parts  the  dimen- 
sions of  the  apparatus  just  described,  it  would  be  easy  to  pro- 
duce much  larger  quantities  of  sodium.  This  idea,  which 
naturally  presented  itself  to  me  at  once,  has  been  the  cause  of 
many  unfruitful  attempts,  into  the  details  of  which  I  will  not 
enter.  I  must,  however,  explain  some  details  which  may  ap- 
pear insignificant  at  first  sight,  but  which  were  necessitated 
during  the  development  of  the  process.  For  instance,  it  will 
perhaps  look  irrational  for  me  to  keep  the  same  sized  outlet 
tubes  and  condensers  that  were  used  with  the  mercury  bottles, 
for  tubes  five  times  as  large ;  but  I  was  forced  to  adopt  this 
arrangement  after  trying  the  use  of  tubes  and  condensers  of  all 
sizes ;  indeed,  it  is  fortunate  for  the  success  of  the  operation 
that  this  was  so,  for  it  became  very  injurious  to  the  workmen 
to  handle  the  large  and  weighty  apparatus  in  the  face  of  a  large 
sodium  flame. 

The  mixture  of  sodium  carbonate  and  carbon  is  made  in  the 
manner  already  described.  I  would  say  again  that  a  previous 
strong  calcination  of  the  materials  presents  a  great  advantage^ 
not  only  because  it  permits  putting  a  much  larger  weight  into 
the  retorts  at  once,  but  also  that,  being  more  compact,  the  mix- 
ture will  not  rise  as  powder  and  be  violently  thrown  out  of  the 



Strongly-heated  retorts.  The  mixture  should  also  be  calcined 
as  needed,  and  used  to  fill  the  tubes  while  still  red  hot.  When 
cold,  uncalcined  mixture  is  used,  it  is  put  into  large  cartridges 
of  thick  paper  or  canvas,  8  centimetres  diameter  and  35  cen- 
timetres long. 

The  furnace  and  tubes  are  shown  in  section  in  Fig.  16.  The 
tubes  T  are  120  centimetres  long,  14  centimetres  inside 
diameter,  and  10  to  12  millimetres  in  thickness.  They  are 
formed  from  one  piece  of  boiler  iron,  bent  and  welded  along 

Fig.  16. 

one  side.  The  iron  plate  P  which  closes  one  end  is  about  2 
centimetres  thick,  and  pierced  on  one  of  its  edges  quite  close 
to  the  side  of  the  cylinder  by  a  hole  in  which  is  screwed  or 
fitted  an  iron  tube,  Z,  5  to  6  centimetres  long  and  15  to  20 
millimetres  inside  diameter,  and  tapering  off  at  the  end  to  fit 
into  the  condenser  neck.  The  other  end  of  the  tube  is  closed 
by  an  iron  plug,  0,  terminated  by  a  knob.  The  welded  side  of 
the  tube  is  kept  uppermost.  These  iron  tubes  should  not,  like 
the  mercury  bottles,  be  heated  in  the  bare  fire ;  it  is  necessary 
to  coat  them  with  a  resistant  luting  which  is  itself  enveloped  by 
a  refractory  jacket  i   centimetre  thick,  22  centimetres  interior 


diameter,  and  the  same  length  as  the  retorts.  This  protection 
is  commenced  by  plastering  the  retorts  over  with  a  mixture  of 
equal  parts  of  raw  clay  and  stove  ashes,  which  have  been  made 
into  a  paste  with  water  and  as  much  sand  worked  into  the  mix- 
ture as  it  will  take  without  losing  its  plasticity,  also  adding 
some  horse  manure.  This  luting  should  be  dried  slowly,  and 
the  tube  thus  prepared  is  introduced  into  the  refractory  jacket, 
the  open  space  between  the  two  being  filled  with  powdered 
refractory  brick.  Finally,  luting  is  put  on  the  iron  plate  P,  so 
that  no  part  of  it  is  exposed  to  the  flame. 

The  furnace  I  have  used  is  a  reverberatory,  but  I  do  not  re- 
commend its  use  without  important  modifications,  because  it 
does  not  realize  all  the  conditions  of  easy  and  economic  heat- 
ing. The  grate  is  divided  into  two  parts  by  a  little  wall  of  re- 
fractory brick,  on  which  the  middle  of  the  reduction  cylinders 
rests.  The  tubes  are  thus  seen  to  be  immediately  over  the  bed 
of  fuel.  The  top  of  the  bridge  is  a  little  higher  than  the  upper 
edge  of  the  cylinders,  this  and  the  very  low  arch  making  the 
flame  circulate  better  all  around  the  tubes.  A  third  cylinder 
might  easily  be  placed  above  these  two,  and  be  heated  satis- 
factorily, without  any  more  fuel  being  burnt.  This  reverbera- 
tory receives  on  its  bed  the  mixtures  to  be  calcined,  placed  in 
cast-iron  or  earthen  pots  according  to  their  composition. 
When  the  furnace  is  kept  going  night  and  day  producing 
sodium,  the  temperature  rises  on  the  bed  to  clear  cherry-red, 
and  experience  has  shown  that  other  reducing  cylinders  might 
be  placed  there,  under  such  conditions,  and  be  heated  suf- 
ficiently for  the  reduction. 

All  that  I  have  said  of  the  manufacture  of  sodium  in  mercury 
bottles  applies  equally  to  its  manufacture  in  cylinders.  The 
only  difference  consists  in  the  charging  and  discharging,  and  I 
have  only  to  add  several  precautions  to  be  taken.  On  intro- 
ducing the  cartridges  containing  uncalcined  mixture,  only  8  to 
9  kilos  can  be  heated  at  once ;  double  as  much  can  be  used  of 
previously-calcined  mixture.  The  plug  0  is  put  in  place,  not 
so  tightly  that  it  cannot  easily  be  taken  out  again ;    a   little 


luting  stops  all  leakages  which  show  themselves.  The  reduc- 
tion lasts  about  four  hours.  When  it  is  finished,  a  little  water  is 
thrown  on  the  plug  0,  and  it  is  easily  loosened  and  removed. 
On  looking  into  the  cylinder,  the  cartridges  are  seen  to  have 
kept  their  shape,  but  have  shrunken  so  much  that  their  diameter 
is  only  about  2  to  3  centimetres ;  they  are  very  spongy.  This 
shows  that  the  mixture  has  not  melted ;  the  remainder  is  prin- 
cipally lime  and  carbon,  and  free  from  sodium  carbonate. 
While  opening  the  cylinder,  a  bright-red-hot  iron  is  thrust  into 
the  outlet  tube  L,  to  keep  dirt  from  getting  into  it,  and  it  is 
kept  in  until  the  charging  is  finished.  The  cartridges  are  put 
in  by  means  of  semi-cylindrical  shovels.  The  sudden  heating 
of  the  mixture  disengages  soda  dust  from  uncalcined  mixtures, 
which  is  very  disagreeable  to  the  workmen.  The  cylinders  are 
closed,  and  when  the  sodium  flame  appears  at  the  outlet  tube 
the  condenser  is  attached,  and  the  operation  proceeds  as 
already  described. 

The  envelopes  of  the  cylinders  are  thick  enough  to  prevent 
the  distillation  of  the  sodium  being  in  any  way  affected  by  the 
accidental  causes  of  cooling  the  fire.  So  when  fresh  fuel  is 
charged  or  the  door  of  the  reverberatory  is  opened,  causing  the 
draft  to  cease  almost  entirely  in  the  fire-place,  the  operation 
should  not  suffer  by  these  intermittences,  provided.that  they  are 
not  too  long  prolonged.  In  short,  when  operating  in  cylinders, 
the  production  of  sodium  is  easier,  less  injurious  to  the  work- 
men, and  less  costly  in  regard  to  labor  and  fuel  than  when 
working  with  mercury  bottles.  At  times,  after  working  a  fort- 
night with  many  interruptions  dangerous  for  the  apparatus,  my 
experiment  has  been  suddenly  ended.  The  furnace  was  intact ; 
the  envelopes  of  the  tubes  were  split  open,  and  the  luting  on 
the  tubes  found  to  be  compact  and  coherent,  but  without  traces 
of  fusion,  showing  perfect  resistance.  The  iron  tubes  mean- 
while had  not  suffered  inside  or  out,  and  seemed  as  though 
they  would  last  indefinitely.  I  attribute  this  success  to  the  par- 
ticular care  given  to  the  composition  of  the  jackets,  and  to  the 
perfection  with  which  the  tubes  had  been  welded.  Only  on 


one  of  the  tubes  was  a  very  slight  crack  found,  on  a  part  not 
the  most  highly  heated,  and  not  sufficient  to  cause  the  tube  to 
be  discarded. 

Tissier  Bros.'  method  of  procedure.  (1856).  As  related  in 
the  historical  treatment  of  the  subject  (p.  13),  Deville  charged 
the  Tissier  Bros,  with  appropriating  from  him  the  process  for 
the  continuous  production  of  sodium  in  cylinders,  which,  as 
just  given,  was  devised  during  the  experiments  at  Javel.  On 
the  other  hand,  the  Tissier  Bros,  asserted  their  right  to  the 
process,  patenting  it,  and  using  it  in  the  works  started  at  Rouen 
in  the  latter  part  of  1855.  The  following  details  are  taken 
from  Tissier's  "  Recherche  de  1' Aluminium,"  only  such  being 
selected  as  supplement  Deville's  description,  which  has  just 
been  given. 

The  sodium  carbonate  is  first  well  dried  at  a  high  temper- 
ature, then  mixed  with  well-dried  pulverized  charcoal  and  chalk, 
ground  to  the  finest  powder,  the  success  of  the  operation  de- 
pending on  the  fineness  of  this  mixture.  The  proportions  of 
these  to  use  are  various.     One  simple  mixture  is  of 

Sodium  carbonate 566 

Coal 244 

Chalk 95 

Coke 95 


Another  contains — 

Sodium  carbonate 615 

Coal 277 

Chalk 108 


The  addition  of  chalk  has  the  object  of  making  the  mixture 
less  fusible  and  more  porous,  but  has  the  disadvantage  that  the 
residue  remaining  in  the  retort  after  the  operation  is  very  im- 
pure, and  it  is  impossible  to  add  any  of  it  to  the  succeeding 
charge ;  and  also,  some  of  it  being  reduced  to  caustic  lime 
forms  caustic  alkali  with  some  sodium  carbonate,  which  is  then 



lost.  WheD  the  mixture  is  well  made  it  is  subjected  to  a  pre- 
limiinary  calcination.  This  is  done  in  cast-iron  cylinders,  two 
of  which  are  placed  side  by  side  in  a  furnace  and  heated  to 
redness  (see  Fig.  17).  This  is  continued  till  all  the  moisture, 
carbonic  acid,  and  any  carburetted  hydrogen  from  the  coal, 
cease  coming  off.  The  mass  contracts,  becomes  white  and 
somewhat  dense,  so  that  a  larger  amount  of  the  mixture  can 
now  be  treated  in  the  retorts  where  the  sodium  is  evolved.  As 
soon  as  the  outcoming  gases  burn  with  a  yellow  flame,  showing 

Fig.  17. 

sodium  coming  ofT,  the  calcination  is  stopped.  The  mixture  is 
then  immediately  drawn  out  on  to  the  stone  floor  of  the  shop, 
where  it  cools  quickly  and  is  then  ready  for  the  next  operation. 
This  calcination  yields  a  mixture  which  without  any  previous 
reactions  is  just  ready  to  evolve  sodium  when  brought  to  the 
necessary  temperature.  This  material  is  made  into  a  sort  of 
cylinder  or  cartridge  and  put  into  the  decomposition  retorts 
(see  Fig.  16).  The  charging  should  be  done  quickly.  The 
final  retorts  are  of  wrought-iron,  since  cast-iron  would  not 
stand  the  heat.  At  each  end  this  retort  is  closed  with  wrought- 
iron  stoppers  and  made  tight  with  fire-clay.  Through  one 
stopper  leads  the  pipe  to  the  condenser,  the  other  stopper  is 
the  one  removed  when  the  retort  is  to  be  recharged.  These 
retorts  are  placed  horizontally  in  rows  in  a  furnace.  Usually 
four  are  placed  in  a  furnace,  preferably  heated  by  gas,  such  as 
the  Siemens   regenerative  furnace  or  Bicheroux,    these  being 


much  more  economical.  In  spite  of  all  these  precautions  the 
retorts  will  be  strongly  attacked,  and  in  order  to  protect  them 
from  the  destructive  action  of  a  white  heat  for  seven  or  eight 
hours  they  are  coated  with  some  kind  of  fire-proof  material. 
The  best  for  this  purpose  is  graphite,  which  is  made  into  cylin- 
ders enclosing  the  retorts,  and  which  can  remain  in  place  till 
the  furnace  is  worn  out.  These  graphite  cylinders  not  only 
protect  the  iron  retorts,  but  prevent  the  diffusion  of  the  gas- 
eous products  of  the  reaction  into  the  hearth,  and  so  support 
the  retorts  that  their  removal  from  the  furnace  is  easily  accom- 
plished. Instead  of  these  graphite  cylinders  the  retorts  may 
be  painted  with  a  mixture  that  melts  at  white  heat  and  so  en- 
amels the  outside.  A  mixture  of  alumina,  sand,  yellow  earth, 
borax,  and  water-glass  will  serve  very  well  in  many  cases.  We 
would  remark  that  the  waste  gases  from  this  furnace  can  be 
used  for  the  calcining  of  the  mixture,  or  even  for  the  reduction 
of  the  aluminium  by  sodium,  where  the  manufacture  of  the 
former  is  connected  with  the  making  of  the  sodium. 

As  for  the  reduction  of  the  sodium,  the  retort  is  first  heated 
to  redness,  during  which  the  stopper  at  the  condenser  end  of 
the  retort  is  left  off.  The  charge  is  then  rapidly  put  in,  and  the 
stopper  at  once  put  in  place.  The  reaction  begins  almost  at 
once  and  the  operation  is  soon  under  full  headway,  the  gases 
evolved  burning  from  the  upper  slit  of  the  condenser  tube  with 
a  flame  a  foot  long.  The  gases  increase  in  volume  as  the 
operation  continues,  the  flame  becoming  yellower  from  sodium 
and  so  intensely  bright  as  to  be  insupportable  to  look  at.  Now 
has  come  the  moment  when  the  workman  must  quickly  adapt 
the  condenser  to  the  end  of  the  tube  projecting  from  the  retort, 
the  joint  being  greased  with  tallow  or  parafHn.  The  sodium 
collects  in  this  in  a  melted  state  and  trickles  out.  The  length 
of  the  operation  varies,  depending  on  the  intensity  of  the  heat 
and  the  quantity  of  the  mixture ;  a  charge  may  sometimes  be 
driven  over  in  two  hours,  and  sometimes  it  takes  eight.  We 
can  say,  in  general,  that  if  the  reaction  goes  on  quickly  a  some- 
what larger  amount  of  sodium  is  obtained.     The  higher  the 


heat  used,  however,  the  quicker  the  retorts  are  destroyed.  The 
operation  requires  continual  attention.  From  time  to  time,  a 
workm-an  with  a  prod  opens  up  the  neck  of  the  condenser, 
but  if  care  is  not  taken  the  metal  overflows ;  if  this  happens, 
the  metal  overflowing  is  thrown  into  some  petroleum,  while 
another  man  replaces  the  condenser  with  an  empty  one.  The 
operation  is  ended  when  the  evolution  of  gas  ceases  and  the 
flame  becomes  short  and  feeble,  while  the  connecting  tube  be- 
tween the  retort  and  condenser  keeps  clean  and  does  not  stop 
up.  As  soon  as  this  occurs,  the  stopper  at  the  charging  end 
is  removed,  the  charge  raked  out  into  an  iron  car,  and  a  new 
charge  being  put  in,  the  operation  continues.  After  several 
operations  the  retorts  must  be  well  cleaned  and  scraped  out. 
The  sodium  thus  obtained  is  in  melted  bits  or  drops,  mixed 
with  carbon  and  sodium  carbonate.  It  must,  therefore,  be 
cleaned,  which  is  done  by  melting  it  in  a  wrought-iron  kettle 
under  paraffin  with  a  gentle  heat,  and  then  casting  it  into  the 
desired  shapes.  The  sodium  is  kept  under  a  layer  of  oil  or 
any  hydrocarbon  of  high  boiling  point  containing  no  oxygen. 
Tissier  gives  the  reaction  as — 


The  sodium  is  condensed,  while  the  carbonic  oxide,  carrying 
over  some  sodium,  burns  at  the  end  of  the  apparatus.  This 
would  all  be  very  simple  if  the  reaction  of  carbonic  oxide  on 
sodium  near  the  condensing  point  did  not  complicate  matters, 
producing  a  black,  infusible  deposit  of  sodium  monoxide 
(Na^O)  and  carbon,  which  on  being  melted  always  give  rise  to 
a  loss  of  sodium. 

Deville's  Improvements  at  La  Glacier e  (1857). 

At  this  works  Deville  tried  the  continuous  process  of  manu- 
facturing sodium  in  cylinders  on  a  still  larger  scale,  with  the  fol- 
lowing results,  as  described  by  Deville  himself: — 

"  We  made  no  change  in  the  composition  of  the  mixtures  used 


from  those  already  described,  or  in  the  form  or  size  of  the  iron 
tubes  or  the  method  of  condensation ;  but  we  worked  with  six 
cylinders  at  a  time  in  a  furnace  similar  to  the  puddling  furnaces 
of  M.  Guadillot,  the  tubes  being  protected  by  refractory  envel- 
opes. The  cylinders  were  so  arranged  on  the  hearth  that  the 
flame  bathed  all  parts  of  their  surface.  A  low  brick  wall  ex- 
tends down  the  centre  of  the  hearth,  supporting  the  middle  of  the 
cylinders,  which  extend  across  it.  The  hearth  is  well  rammed 
with  refractory  sand,  and  the  space  between  it  and  the  bottom 
of  the  cylinder  serves  as  a  passage-way  for  most  of  the  flame. 

"  Our  six  cylinders  worked  satisfactorily  for  five  days.  We 
were  able  to  observe  that  they  were  all  heated  with  remarkable 
uniformity,  and  that  the  heat  was  sufficient  all  round  them.  It 
also  appeared  that  the  rear  end  of  the  cylinders  required  only 
a  hermetic  seal.  Indeed,  as  soon  as  the  operation  was  well 
under  way  and  sodium  distilling  off,  some  of  it  condensed  and 
oxidized  in  the  cool  parts  of  the  apparatus,  forming  a  sort  of 
plug  of  carbonate  and  carbides  of  sodium,  which  the  vapor  and 
gases  could  no  longer  penetrate.  We  were  thus  able  for  a 
long  time  to  distil  sodium  away  from  one  of  our  tubes  which 
was  entirely  opened  at  the  rear. 

"  This  new  furnace  worked  so  well  that  we  were  hopeful  of 
complete  success,  when  an  accident  happened  which  compelled 
the  stopping  of  the  experiment.  The  iron  tubes  had  been 
ordered  1.20  metres  long,  the  size  of  the  hearth  calculated  ac- 
cordingly, but  they  were  delivered  to  us  only  1.05  metres  long. 
We  made  use  of  these,  with  the  result  that  the  rear  ends  be- 
came red-hot  during  the  operation  and  allowed  sodium  vapors 
to  leak  through.  These  leaked  through  the  luting,  and  escap- 
ing into  the  furnace,  melted  the  envelopes  very  rapidly. 

"In  another  attempt,  in  which  this  fault  was  avoided,  we  were 
unsuccessful  because  the  envelopes  gave  way  at  the  first  heat- 
ing up,  both  they  and  the  iron  tubes  being  of  inferior  quality. 
We  were  considerably  inconvenienced  by  the  failure  of  these 
experiments,  which  caused  considerable  expense  and  gave  no 
very  definite  results.     Just  then  a  new  sort  of  apparatus  was 


devised,  a  description  of  which  is  given  later  on.  It  will  be 
seen  that  we  were  compelled  to  employ  tubes  of  very  small 
value,  so  that  their  destruction  in  case  of  accident  involved  no 
great  loss,  and  to  heat  each  one  by  an  independent  fire,  so  that 
the  stoppage  or  destruction  of  one  cylinder  would  not  necessitate 
the  stoppage  or  endanger  the  safety  of  the  neighboring  ones." 

Cast-iron  vessels.  Deville  tried  at  La  Glaciere,  as  well  as  at 
Javel,  to  utilize  cast-iron  vessels  for  producing  sodium.  Deville 
states  the  difficulties  which  caused  their  use  to  be  unsuccessful 
to  be  as  follows  : 

"The  result  was  always  unfavorable.  Sodium  is  obtained,  but 
as  soon  as  its  production  becomes  rapid  the  vessel  melts  and 
the  operation  is  quickly  ended.  This  follows  because  the  tem- 
perature necessary  for  the  production  of  the  metal  is  far  from 
being  sufficient  for  producing  it  in  large  quantities  at  once  ;  and 
we  know  that  this  is  the  one  condition  for  condensing  the  so- 
dium well  and  obtaining  it  economically.  This  observation  led 
me  to  think  that  by  diminishing  very  much  the  temperature  of 
the  furnace,  large  apparatus  of  cast-iron  with  large  working 
surface  could  be  used,  thus  making  at  a  time  a  large  amount  of 
metallic  vapor  which  could  be  condensed  in  recipients  of  ordi- 
nary size.  The  whole  large  apparatus  would  thus  have  the  out- 
put of  a  smaller  one  worked  at  a  higher  temperature.  My  ex- 
perience has  shown  me  that  in  large-sized  tubes  heated  to  a 
low  temperature  there  is  formed  in  a  given  time  about  as  much 
sodium  as  from  a  single  mercury  bottle  at  a  much  higher  heat. 
This  is  the  reason  why  larger  condensers  are  not  necessary 
with  the  larger  tubes.  Before  knowing  this  fact,  I  tried  a  large 
number  of  useless  experiments  to  determine  the  size  of  con- 
densers suitable  for  large  apparatus.  It  is  on  this  principle 
that  I  have  long  been  endeavoring  to  make  sodium  without 
working  at  high  temperatures,  and  using  less  costly  and  more 
easily  protected  apparatus." 

Improvements  used  at  Nanterre  (1859). 
The  method  used  here  was  exactly  that  already  described, 


the  improvements  being  solely  in  details  of  the  apparatus. 
These  are  described  by  Deville  as  follows : — 

"  The  experiments  made  at  Javel  and  the  continuous  process 
used  at  Glaciere  have  shown  us  in  the  clearest  manner  the  ab- 
solute necessity  of  efficient  protection  for  the  iron  cylinders,  for 
without  this  protection  the  method  cannot  be  practiced  with 
economy.  Further,  experiments  in  this  direction  are  very 
costly,  for  the  failure  of  a  tube  stops  the  working  of  a  large 
number  of  cylinders,  and  often  compromises  the  brick-work  of 
the  furnace  itself.  We  therefore  came  to  the  conclusion  that 
for  making  the  small  quantity  of  sodium  we  required,  300  to  500 
kilos  a  month,  it  would  be  better  to  employ  smaller  apparatus, 
independent  of  each  other  and  easy  to  replace. 

"  The  iron  tubes  are  made  of  thinner  iron  and  at  very  little  ex- 
pense, by  taking  a  sheet  of  iron,  curving  it  into  a  cylinder  and 
riveting  the  seam.  This  tube  resembles  very  closely  those 
used  at  Javel,  shown  in  Fig.  16,  but  of  smaller  dimensions.  It 
is  closed  at  each  end  by  cast-iron  plugs,  one  of  which  has  a 
hole  for  the  outlet  tube.  These  cylinders  are  filled  with  sodium 
mixture  and  placed  in  furnaces  of  the  form  of  Fig.  10,  except  it 
is  necessary  to  have  openings  in  the  back  and  front  of  the  fur- 
nace so  that  the  cast-iron  plugs  closing  the  cylinders  may  be 
outside,  to  prevent  their  melting.  We  used  coke  at  first  for 
fuel,  fed  around  the  cylinders,  but  M.  Morin  has  since  placed  the 
tubes  out  of  direct  contact  with  the  fuel,  uses  soft  coal,  and  heats 
the  tubes  by  contact  with  the  flame  and  by  radiation.  In  the 
latest  form  used,  two  cylinders  are  placed  in  each  furnace,  and, 
in  general,  they  serve  for  two  or  three  operations.  All  that  has 
been  said  in  connection  with  the  manufacture  in  mercury  bot- 
tles is  immediately  applicable  to  the  manufacture  in  cylinders 
of  this  kind,  the  capacity  of  which  may  vary  from  two  to  six  or 
eight  litres,  without  any  change  in  the  manner  of  using  them. 
We  have,  however,  adopted  altogether  condensers  of  cast-iron. 
The  neck  is  cylindrical  and  belongs  only  to  one-half  of  the  ap- 
paratus, the  neck  end  of  the  other  plate  being  beveled  and  fit- 
ting closely  against  a  recess  in  the  other  plate." 


The  foregoing  shows  the  sodium  industry  as  it  was  perfected 
by  Deville,  in  1859,  and  as  it  remained  for  twenty-five  years 
without  sensible  change.  The  cost  of  sodium  by  this  process 
is  stated  to  have  been,  in  1872,  as  follows: — 

Manufacture  of  one  kilo  of  sodium. 

Soda 9.35  kilos  @  32       fr.  per  100  kilos  =  3  fr.    9  cent. 

Coal 74.32    "      "     1.40"    "      "      "     =  I   "    4    " 

Wages 3  "  73    " 

Expenses 3  "  46     " 

Total 1 1  fr.  32  cent. 

which  is  equal  to  $1  per  lb.  The  larger  part  of  the  expense 
account  is  the  cost  of  retorts  or  tubes  in  which  the  operation 
takes  place,  and  which  are  so  quickly  destroyed  that  the  re- 
placing of  them  forms  nearly  one-quarter  of  the  cost  of  the 

Minor  Improvements  (185 9- 1888). 

An  experiment  made  by  Deville  in  1864*  is  of  considerable 
interest  in  connection  with  some  more  recent  processes.  Guy 
Lussac  and  Thenard  having  observed  that  caustic  potash  is  re- 
duced by  iron,  Deville  took  a  mercury  bottle  with  an  aperture 
above  and  one  below,  to  which  was  fitted  an  iron  tube  and  a 
sodium  condenser.  Finely  divided  iron,  reduced  by  hydrogen, 
was  put  into  the  bottle,  and  when  red  hot,  caustic  soda  was  in- 
troduced through  the  upper  aperture.  The  iron  was  strongly 
acted  upon,  and  in  less  than  20  minutes  Deville  obtained  y^  a 
kilo  of  pure  sodium.  The  reduction  was  stopped  by  a  mixture 
of  soda  and  iron  oxide  filling  up  the  lower  opening.  The  ar- 
rangement and  reactions  suggest  strongly  some  later  processes. 
Why  Deville  did  not  continue  on  this  line,  I  cannot  say. 

R.  Wagnerf  uses  paraffin  in  preference  to  paraffin  oil  in 
which  to  keep  the  sodium  after  making  it.  Only  pure  paraffin, 
which  has  been  melted  a  long  time  on  a  water-bath,  and  all  its 
water  driven  off,  can  be  used.     The  sodium  to  be  preserved  is 

*  Lef  ons  de  Chemie,  1864-5,  P-  336-  +  Dingier,  1883,  p.  252. 


dipped  in  the  paraffin  melted  on  a  water-bath,  and  kept  at  no 
higher  heat  than  55°  C,  and  the  metal  is  thereby  covered  with  a 
thick  coat  of  paraffin  which  protects  it  from  oxidation,  and  may 
then  be  put  up  in  wooden  or  paper  boxes.  When  the  metal  is 
to  be  used,  it  is  easily  freed  from  paraffin  by  simply  warming 
it,  since  sodium  melts  at  95°  to  96°  C,  and  the  paraffin  at  50° 
to  60°. 

The  reduction  of  potassium  carbonate  by  carbon  requires  a 
much  less  degree  of  heat  than  that  of  sodium  carbonate,  and 
therefore  many  attempts  have  been  made  to  reduce  potassium 
and  sodium  together,  under  circumstances  where  sodium  alone 
would  not  be  reduced.  Dumas*  added  some  potassium  car- 
bonate to  the  regular  sodium  mixture;  and  separated  the 
sodium  and  potassium  from  each  other  by  a  slow,  tedious  oxi- 
dation. R.  Wagnerf  made  a  similar  attempt.  He  says  that 
not  only  does  the  reduction  of  both  metals  from  a  mixture  of 
their  carbonates  with  carbon  work  easier  than  sodium  carbonate 
alone  with  carbon,  but  even  caustic  soda  may  be  used  with 
potassium  carbonate  and  carbon.  Also,  the  melting  point  of 
potassium  and  sodium  alloyed  is  much  lower  than  that  of  either 
one  alone,  in  consequence  of  which  their  boiling  point  and  the 
temperature  required  for  reduction  are  lower. 

J.  B.  Thompson  and  W.  WhiteJ  specify  mixing  dry  sodium 
carbonate  with  a  liquid  carbonaceous  material,  preferably  tar, 
driving  off  all  volatile  matter  in  iron  pots  at  a  low  heat,  and 
then  distilling  in  a  tubular  fire-clay  retort  connected  with  a 
tightly-closed  receiver  containing  a  little  paraffin  oil  to  ensure  a 
non-oxiding  atmosphere,  and  also  provided  with  a  small  escape 
pipe  for  carbonic  oxide.  This  process  gave  great  prospects  of 
success  when  tried  in  the  laboratory,  but  on  a  manufacturing 
scale  it  failed  for  the  reason  (assigned  by  Mr.  Thompson)  that 
the  sheet-iron  tray,  designed  to  keep  the  material  from  attack- 
ing the  retort,  absorbed  carbon  at  about  1000°  C.  and  fused, 
after  which  no  sodium  was  produced,  since  the  material  took 

*  Handbuch  der  Angewandten  Chemie,  1830,  ii.  345. 

t  Dingier,  143,  343-  J  English  Patent  8426,  June  11,  1887. 


up  silica  from  the  retort,  absorbing  so  much  that  the  carbon  no 
longer  decomposed  it. 

H.  S.  Blackmore,*  of  Mount  Vernon,  U.  S.  A.,  patents  the 
following  process  of  obtaining  sodium:  — 

Calcium  hydrate 273^  parts. 

B  erric  oxide 31  " 

Dry  sodium  carbonate 31  " 

Charcoal   loj!^      " 

are  intimately  mixed  and  subjected  to  a  red  heat  for  20  min- 
utes, afterwards  to  a  white  heat.  Caustic  soda  is  first  produced, 
the  carbon  reduces  the  ferric  oxide,  producing  iron,  which  in 
its  turn  reduces  the  caustic  soda,  and  sodium  vapors  distil. 
The  residue  consists  of  ferric  oxide  and  lime,  and  is  slaked  and 
used  over. 

O.  M.  Thowlessf  of  Newark,  N.  J.,  claims  to  place  a  retort  in 
a  furnace,  providing  it  on  one  side  with  an  arm  through  which 
carboniferous  material  can  be  supplied,  on  the  other  side  with  a 
similar  arm  (surrounded  by  flues),  into  which  caustic  soda  or 
sodium  carbonate  is  charged — a  valve  controlling  their  flow  into 
the  retort.  Outside  the  furnace  and  on  top  of  it  is  a  flat  con- 
denser into  which  the  sodium  vapor  passes. 

G.  A.  JarvisI  patents  the  replacement  of  the  iron  tubes  or 
crucibles  used  in  the  manufacture  of  sodium,  by  fire-clay  ap- 
paratus lined  with  basic  material,  such  as  strongly  burnt  mag- 
nesia with  10  per  cent,  of  fluorspar. 

Castner's  Process  (1886). 
The  first  public  announcement  of  this  process  was  through 
one  of  the  New  York  daily  journals,^  and  as  the  tone  of  the 
article  is  above  that  of  the  usual  newspaper  reports,  and  the 
expectations  contained  in  it  were  subsequently  more  than 
realized,  we  cannot  better  introduce  a  description  of  this  process 
than  by  quoting  the  paragraph  referred  to :  — 

♦English  Patent  15 156,  Oct.  22,  1888.  f  English  Patent  12486  (1887). 

X  English  Patent  4842,  March  31,  1888.  §  New  York  World,  May  16,  1886. 


"When  sodium  was  reduced  in  cost  to  $1.50  per  lb.  it  was 
thought  to  have  touched  a  bottom  figure,  and  all  hope  of  mak- 
ing it  any  cheaper  seemed  fruitless.  This  cheapening  was  not 
brought  about  by  any  improved  or  new  process  of  reduction, 
but  was  owing  simply  to  the  fact  that  the  aluminium  industry 
required  sodium,  and  by  making  it  in  large  quantities  its  cost 
does  not  exceed  the  above-mentioned  price.  The  retail  price 
is  now  $4.00  per  lb.  The  process  now  used  was  invented  by 
Briinner,  in  1808,  and  up  to  the  present  time  nothing  new  or 
original  has  been  patented  except  three  or  four  modifications  of 
his  process  which  have  been  adopted  to  meet  the  requirements 
of  using  it  on  a  large  scale.  Mr.  H.  Y.  Castner,  whose  labora- 
tory is  at  218  West  Twentieth  Street,  New  York,  has  the  first 
patent  ever  granted  on  this  subject  in  the  United  States,  and 
the  only  one  taken  out  in  the  world  since  1808.  Owing  to 
negotiations  being  carried  on,  Mr.  Castner  having  filed  appli- 
cations for  patents  in  various  foreign  countries,  but  not  having 
the  patents  granted  there  yet,  we  are  not  at  liberty  to  state  his 
process  fully.  The  metal  is  reduced  and  distilled  in  large  iron 
crucibles,  which  are  raised  automatically  through  apertures  in 
the  bottom  of  the  furnace,  where  they  remain  until  the  reduc- 
tion is  completed  and  the  sodium  distilled.  Then  the  crucible 
is  lowered,  a  new  one  containing  a  fresh  charge  is  substituted 
and  raised  into  the  furnace,  while  the  one  just  used  is  cleaned 
and  made  ready  for  use  again.  The  temperature  required  is 
very  moderate,  the  sodium  distillling  as  easy  as  zinc  does  when 
being  reduced.  Whereas  by  previous  processes  only  one-third 
of  the  sodium  in  the  charge  is  obtained,  Mr.  Castner  gets 
nearly  all,  for  the  pots  are  nearly  entirely  empty  when  with- 
drawn from  the  furnace.  Thus  the  great  items  of  saving  are 
two  or  three  times  as  much  metal  extracted  from  a  given 
amount  of  salt,  and  cheap  cast  iron  crucibles  used  instead  of 
expensive  wrought-iron  retorts.  Mr.  Castner  expects  to  pro- 
duce sodium  at  25  cents  per  lb.,  thus  solving  the  problem  of 
cheap  aluminium,  and  with  it  magnesium,  silicon,  and  boron, 
all  of  which  depend  on  sodium  for  their  manufacture.     Thus 


the  production  of  cheap  sodium  means  much  more  than  cheap 
aluminium.  Mr.  Castner  is  well  known  in  New  York  as  a 
chemist  of  good  standing,  and  has  associated  with  him  Mr.  J. 
H.  Booth  and  Mr.  Henry  Booth,  both  well  known  as  gentlemen 
of  means  and  integrity." 

The  following  are  the  claims  which  Mr.  Castner  makes  in 
his  patent:* 

1.  In  a  process  for  manufacturing  potassium  or  sodium,  per- 
forming the  reduction  by  diffusing  carbon  in  a  body  of  alkali 
in  a  state  of  fusion  at  moderate  temperatures. 

2.  Performing  the  reduction  by  means  of  the  carbide  of.  a 
metal  or  its  equivalent. 

3.  Mechanically  combining  a  metal  and  carbon  to  increase 
the  weight  of  the  reducing  material,  and  then  mixing  this  pro- 
duct with  the  alkali  and  fusing  the  latter,  whereby  the  reducing 
material  is  held  in  suspension  throughout  the  mass  of  fused 

4.  Performing  the  deoxidation  by  the  carbide  of  a  metal  or 
its  equivalent. 

For  an  explanation  of  the  principles  made  use  of  in  the 
above  outlined  process  we  will  quote  from  a  lecture  delivered 
by  Mr.  Castner  at  the  Franklin  Institute,  Philadelphia,  October 
1 2th,  1886.  That  Institution  has  since  bestowed  on  Mr.  Cast- 
ner one  of  its  gold  medals  as  a  recognition  of  the  benefit  to 
science  accruing  from  his  invention. 

"  In  the  ordinary  sodium  process,  lime  is  added  to  the  reduc- 
ing mixture  to  make  the  mass  refractory,  otherwise  the  alkali 
would  fuse  when  the  charge  is  highly  heated,  and  separate  from 
the  light,  infusible  carbon.  The  carbon  must  be  in  the  propor- 
tion to  the  sodium  carbonate  as  four  is  to  nine,  as  is  found 
needful  in  practice,  so  as  to  assure  each  particle  of  soda  in  the 
refractory  charge  having  an  excess  of  carbon  directly  adjacent 
or  in  actual  contact.  Notwithstanding  the  well-known  fact  that 
sodium  is  reduced  from  its  oxide  at  a  degree  of  heat  but  slightly 
exceeding  the  reducing  point  of  zinc  oxide,  the  heat  necessary 

*  U.  S.  Pat.  No.  342,897,  June  i,  1886.     Hamilton  Y.  Castner,  New  York, 


to  accomplish  reduction  by  this  process  and  to  obtain  even 
one-third  of  the  metal  in  the  chai-ge,  closely  approaches  the 
melting  point  of  wrought-iron. 

"  In  my  process,  the  reducing  substance,  owing  to  its  com- 
position and  gravity,  remains  below  the  surface  of  the  molten 
salt,  and  is,  therefore,  in  direct  contact  with  fused  alkali. 
The  metallic  coke  of  iron  and  carbon  contains  about  30  per 
cent,  carbon  and  70  per  cent,  iron,  equivalent  to  the  formula 
FeCj.  I  prefer  to  use  caustic  soda,  on  account  of  its  fusibility, 
and  mix  with  it  such  quantity  of  so-called  '  carbide '  that  the 
carbon  contained  in  the  mixture  shall  not  be  in  excess  of  the 
amount  theoretically  required  by  the  following  reaction:  — 

3NaOHf  FeC,=--3Na4-Fe  +  CO  f  CO.+sH  ; 

or,  to  every  100  lbs.  of  pure  caustic  soda,  75  lbs.  of  'carbide,' 
containing  about  22  lbs.  of  carbon. 

"  The  necessary  cover  for  the  crucible  is  fixed  stationary  in 
each  chamber,  and  from  this  cover  a  tube  projects  into  the  con- 
denser outside  the  furnace.  The  edges  of  the  cover  are  convex, 
those  of  the  crucible  concave,  so  that  when  the  crucible  is  raised 
into  position  and  held  there,  the  tight  joint  thus  made  prevents 
all  leaking  of  gas  or  vapor.  Gas  is  used  as  fuel,  and  the  re- 
duction begins  towards  1000°  C.  As  the  dharge  is  fused,  the 
alkali  and  reducing  material  are  in  direct  contact,  and  this  fact, 
together  with  the  aid  rendered  the  carbon  by  the  fine  iron,  in 
withdrawing  oxygen  from  the  soda,  explains  why  the  reduction  is 
accomplished  at  a  moderate  temperature.  Furthermore,  by 
reducing  from  a  fused  mass,  in  which  the  reducing  agent  re- 
mains in  suspension,  the  operation  can  be  carried  on  in  crucibles 
of  large  diameter,  the  reduction  taking  place  at  the  edges  of  the 
mass,  where  the  heat  is  greatest,  the  charge  flowing  thereto  from 
the  centre  to  take  the  place  of  that  reduced. 

"  I  am  enabled  to  obtain  fully  90  per  cent,  of  the  metal  in  the 
charge,  instead  of  30  per  cent,  as  formerly.  The  crucibles, 
after  treatment,  contain  a  little  carbonate  of  soda,  and  all  the 
iron   of  the  'carbide'  still  in  a  fine  state  of  division,  together 


with  a  small  percentage  of  carbon.  These  residues  are  treated 
with  warm  water,  the  solution  evaporated  to  recover  the  car- 
bonate of  soda,  while  the  fine  iron  is  dried,  and  used  over  again 
for  'carbide.'  " 

Mr.  Castner  having  demonstrated  in  his  New  York  laboratory 
the  success  of  his  process,  went  to  England,  and  for  several 
months  during  the  winter  of  1886-7  was  engaged  in  building 
and  working  a  large  sodium  furnace.  This  was  successfully  car- 
ried out  near  London,  the  inventor  being  assisted  by  Mr.  J. 
MacTear,  F.  C.  S.,  who,  in  March,  1887,  read  a  description  of 
this  furnace  and  the  results  obtained  before  the  Society  of 
Chemical  Industry.  During  the  working  of  this  furnace  it  was 
inspected  by  many  chemical  and  metallurgical  authorities,  who 
were  completely  satisfied  as  to  its  success.  As  the  furnace 
then  described  differed  in  a  few  details  from  the  one  just  re- 
ferred to,  it  may  be  well  to  extract  the  essential  particulars  from 
Mr.  MacTear's  paper — on  the  ground  that  the  importance  of 
this  invention  justifies  a  complete  discussion  of  its  develop- 

"  Since  Mr.  Castner's  paper  upon  his  process,  which  was 
read  before  the  Franklin  Institute  of  Philadelphia,  October  12, 
1886,  several  slight  changes  in  the  mode  of  carrying  on  this 
process  have  been  made.  These  have  been  brought  about  by 
the  experience  gained  from  the  actual  working  of  the  process 
upon  a  commercially  large  scale. 

"The  reactions  by  which  the  sodium  is  produced  are  some- 
what difficult  to  describe,  as  they  vary  somewhat  according  to 
the  mixture  of  materials  and  temperature  employed  in  the  re- 
duction. The  mixture  and  temperature  which  it  is  now  pre- 
ferred to  use  is  represented  by  the  reaction : — 

6NaH0  +  FeC2=  2Na2CO,  +  6H  +  Fe  +  zNa. 

"  In  place  of  using  an  actual  chemical  compound  of  iron  and 
carbon,  as  expressed  by  the  above  reaction,  a  substitute  or 
equivalent  is  prepared  as  follows  :  To  a  given  quantity  of  melted 
pitch  is  added  a  definite  proportion  of  iron  in  a  fine  state  of 


division.  The  mixture  is  cooled,  broken  up  into  lumps,  and 
cooked  in  large  crucibles,  giving  a  metallic  coke  consisting  of 
carbon  and  iron,  the  proportions  of  each  depending  upon  the 
relative  quantities  of  pitch  and  iron  used.  This  metallic  coke, 
after  being  finely  ground,  provides  a  substance  having  the  iron 
and  carbon  in  a  like  proportion  to  an  iron  carbide,  and  from 
which  neither  the  iron  nor  carbon  can  be  separated  by  mechan- 
ical means.  The  fine  iron  is  conveniently  prepared  by  passing 
carbonic  oxide  and  hydrogen  in  a  heated  state,  as  obtained 
from  an  ordinary  gas  producer,  over  a  mass  of  oxide  of  iron 
commercially  known  as  'purple  ore,'  heated  to  a  temperature 
of  about  500°  C. 

"  In  producing  sodium,  caustic  soda  of  the  highest  obtain- 
able strength  is  used,  and  there  is  mixed  with  it  a  weighed 
quantity  of  the  so-called  '  carbide,'  sufficient  to  furnish  the 
proper  amount  of  carbon  to  carry  out  the  reaction  indicated 
above.  The  crucibles  in  which  this  mixture  is  treated  are  made 
of  cast-steel,  and  are  capable  of  containing  a  charge  of  15  lbs. 
of  caustic  soda,  together  with  the  proper  proportion  of  the 
•  carbide.' 

"After  charging  a  crucible  with  the  above  mixture,  it  is 
placed  in  a  small  furnace  where  it  is  kept  at  a  low  heat  for 
about  thirty  minutes,  during  which  time  the  mass  fuses,  boils 
violently,  and  a  large  part  of  the  hydrogen  is  expelled  by  the 
combined  action  of  the  iron  and  carbon,  the  '  carbide,'  owing 
to  its  gravity,  remaining  in  suspension  throughout  the  fused 
soda.  At  the  end  of  the  time  stated,  the  contents  of  the  cru- 
cible have  subsided  to  a  quiet  fusion.  The  crucible  is  then 
lifted  by  a  pair  of  tongs  on  wheels  and  placed  upon  the  plat- 
form of  the  elevating  gear,  as  shown  in  the  drawing,  (Fig.  18) 
and  raised  to  its  position  in  the  heating  chamber  of  the  main  dis- 
tilling furnace.  The  cover  which  remains  stationary  in  the  fur- 
nace has  a  convex  edge,  while  the  crucible  has  a  groove  round  the 
edge  into  which  the  edge  of  the  cover  fits.  A  little  powdered 
lime  is  placed  in  the  crucible  groove  just  before  it  is  raised,  so 
that  when  the  edges  of  the  cover  and  crucible  come  together 



they  form  a  tight  joint,  and  at  the  same  time  will  allow  the 
crucible  to  be  lowered  easily  from  the  chamber  when  the  ope- 
ration is  finished,  to  give  place  to  another  containing  a  fresh 
charge.  From  the  cover  projects  a  slanting  tube  (see  Fig.  18), 
connected  with  the  condenser.  The  condenser  is  provided 
with  a  small  opening  at  the  further  end  to  allow  the  escape  of 
hydrogen,  and  has  also  a  rod  fixed  (as  shown),  by  means  of 
which  any  obstruction  which  may  form  in  the  tube  during  dis- 

FlG.  18. 

tillation  may  be  removed.  After  raising  a  crucible  in  its  place 
in  the  furnace,  the  hydrogen  escaping  from  the  condenser  is 
lighted,  and  serves  to  show  by  the  size  of  the  flame  how  the 
operation  is  progressing  in  the  crucible,  the  sodium  actually 
distilling  soon  after  the  crucible  is  in  its  place.  The  temper- 
ature of  the  reduction  and  distillation  has  been  found  to  be 
about  823°  C.  The  gas  coming  off  during  the  first  part  of  the 
distillation  has  been  analyzed  and  found  to  consist  of  pure 
hydrogen.  Analysis  of  the  gas  disengaged  when  the  ope- 


ration  was  almost  completed,  gave  as  a  result,  hydrogen  95  per 
cent.,  carbonic  oxide  5  per  cent.  It  has  been  found  advisable 
to  use  a  little  more  'carbide'  than  the  reaction  absolutely  re- 
quires, and  this  accounts  for  the  presence  of  the  small  quantity 
of  carbonic  oxide  in  the  expelled  gas,  the  free  carbon  acting 
upon  the  carbonate  formed  by  the  reaction,  thus  giving  off  car- 
bonic oxide  and  leaving  a  very  small  percentage  of  the  residue 
in  the  form  of  peroxide  of  sodium.  This  small  amount  of  car- 
bonic oxide  rarely  combines  with  any  of  the  sodium  in  the 
tube,  and  so  the  metal  obtained  in  the  condensers  is  pure,  and 
the  tubes  never  become  choked  with  the  black  compound.  In 
the  preparation  of  potassium  a  little  less  '  carbide'  is  used  than 
the  reaction  requires ;  thus  no  carbonic  oxide  is  given  off,  and 
all  danger  attached  to  the  making  of  potassium  is  removed. 
After  the  reduction  and  distillation  the  crucible  is  lowered  from 
the  furnace  and  the  contents  poured  out,  leaving  the  crucible 
ready  to  be  recharged.  The  average  analyses  of  the  residues 
show  their  composition  to  be  as  follows:  — 

Carbonate  of  soda 77  per  cent. 

Peroxide  of  sodium 2       " 

Carbon 2       " 

Iron 19       " 

"  The  average  weight  of  these  residues  from  operating  upon 
charges  of  15  lbs.  caustic  soda  and  5^  lbs.  of  carbide  is  16 
lbs.  These  residues  are  treated  either  to  produce  pure  crystal 
lized  carbonate  of  soda  or  caustic  soda,  and  the  iron  is  recov- 
ered and  used  again  with  pitch  in  the  formation  of  the  '  car- 
bide.' From  this  residue  weighing  16  lbs.,  is  obtained  13  lbs. 
of  anhydrous  carbonate  of  soda,  equivalent  to  9.4  lbs.  caustic 
soda  of  76  per  cent. 

"  Operating  upon  charges  as  above  mentioned  the  yield-  has 
been — 

Sodium,  actual 2.50  lbs.     Theory    2.85  lbs. 

Soda  carbonate,  actual 13.00  lbs.  "       13.25  lbs. 

"  The  average  time  of  distillation  in  the  large  furnace  has 


been  i  hour  30  minutes,  and  as  the  furnace  is  arranged  for 
three  crucibles,  45  lbs.  of  caustic  soda  are  treated  every  90 
minutes,  producing  7^  lbs.  of  sodium  and  39  lbs.  of  carbonate 
of  soda.  The  furnace  is  capable  of  treating  720  lbs.  of  caustic 
soda  daily,  giving  a  yield  in  24  hours  of  120  lbs.  of  sodium  and 
624  lbs.  of  anhydrous  carbonate  of  soda.  The  furnace  is  heated 
by  gas  which  is  supplied  by  a  Wilson  Gas  Producer,  consuming 
I  cwt.  of  fuel  per  hour.  The  small  furnace  in  which  the 
crucibles  are  first  heated  requires  about  J^  cwt.  per  hour.  The 
following  estimate  of  cost,  etc.,  is  given  from  the  actual  running 
of  the  furnace  working  with  the  above  charges  for  24  hours : — 

£  ^.  d. 

720  lbs.  of  caustic  soda  @  ;^i  i  per  ton 3  10  10 

1 50  lbs.  of  "  carbide  "  @  yd^d.  per  lb o  6  4 

Labor I  o  o 

Fuel o  17  o 

Re-converting  624  lbs.  of  carbonate  into  caustic,  at  a  cost 

of  about  £^  per  ton  on  the  caustic  produced,  say  ...    I  o  o 

Total 6     14       2 

Deducting  value  of  475  lbs.  of  caustic  recovered 2       6       8 

Cost  of  120  lbs.  of  sodium ^4       7       6 

Cost  per  pound,  83^</. 

"  Regarding  the  item  of  cost  relating  to  the  damage  caused 
to  the  crucibles  by  the  heat,  this  question  has  been  very  care- 
fully gone  into,  some  of  the  crucibles  have  been  used  upwards 
of  fifty  times,  and  from  present  indications  of  their  condition 
there  is  no  doubt  that  they  can  continue  to  be  used  at  least  150 
times  more  before  they  become  unfit  for  further  use.  In  con- 
sidering 200  operations  to  be  the  life  of  a  crucible,  the  item  of 
damage  or  wear  and  tear  amounts  to  less  than  \d.  per  lb.  on 
the  sodium  produced;  and  if  we  take  the  furnace  tear  and  wear 
at  the  same  rate  of  \d.  per  lb.,  we  will  see  that  the  tear  and 
wear  of  plant  is  only  one-twelfth  of  that  incurred  in  the  ordi- 
nary propess.  It  is  upon  these  facts  that  Mr.  Castner  bases 
his  claim  to  be  able  to  produce  sodium  by  Jiis-  process  upon 
the  large  scale,  at  a  cost  of  less  than   15.  per  lb.     The  advan- 


tages  of  this  process  will  be  apparent  to  any  one  at  all  familiar 
with  the  manufacture  of  these  metals  as  conducted  heretofore. 
The  first  and  most  important  end  gained  is  their  cheap  produc- 
tion, and  this  is  owing  chiefly  to  the  low  heat  at  which  the 
metals  are  produced,  the  quickness  of  the  operation,  non- clog- 
ging of  the  conveying  tubes,  and  a  very  small  waste  of  mate- 
rials. The  process  furthermore  admits  of  being  carried  on 
upon  a  very  large  scale ;  in  fact,  it  is  intended  ultimately  to  in- 
crease the  size  of  the  crucible  so  as  to  make  the  charges  con- 
sist of  50  lbs.  of  caustic  soda.  Crucibles  of  cast  iron  have 
been  found  quite  suitable,  and  it  is  intended  in  future,  to  use 
crucibles  made  of  this  material  in  place  of  the  more  expensive 

Immediately  on  the  demonstration  of  this  success,  a  company 
was  formed  to  unite  Mr.  Castner's  sodium  process  with  Mr. 
Webster's  improvements  in  the  production  of  aluminium  chlor- 
ide. The  Aluminium  Co.,  Ltd.,  first  appeared  before  the  public 
in  June,  1887,  and  at  the  first  meeting  in  the  following  Septem- 
ber it  was  decided  to  build  works  at  once.  These  were  begun 
at  Oldbury,  near  Birmingham,  and  were  in  working  operation 
by  the  end  of  July,  1888.  The  furnaces  here  erected  were 
larger  than  the  one  just  described,  and  altogether  had  a  pro- 
ducing capacity  of  nearly  a  ton  of  sodium  a  day.  The  follow- 
ing details  respecting  this  plant  and  its  working  are  taken 
mostly  from  an  address  delivered  before  the  Society  of  Arts, 
March  13,  1889,  by  Mr.  William  Anderson,  and  from  a  dis- 
course at  the  Royal  Institution,  May  3,  1889,  by  Sir  Henry 
Roscoe,  president  of  the  company. 

There  are  four  large  sodium  furnaces,  each  holding  five  pots 
or  crucibles,  and  heated  by  gas,  applied  on  the  regenerative 
principle.  A  platform  about  five  feet  above  the  floor  allows 
the  workmen  to  attend  to  the  condensers,  while  the  lifts  on 
which  the  pots  are  placed  sink  level  with  the  floor.  The 
crucibles  used  are  egg-shaped,  about  18  inches  diameter  at 
their  widest  part  and  24  inches  high ;  when  joined  to  the  cover 
the  whole  apparatus  is  about  3  feet  in  height.     The  covers 


have  vertical  pipes  passing  through  the  top  of  the  furnace, 
forming  a  passage  for  the  introduction  of  part  of  the  charge, 
and  also  a  lateral  pipe  connecting  with  the  condenser.  The 
whole  cover  is  fixed  immovably  to  the  roof  of  the  furnace  and 
is  protected  by  brickwork  from  extreme  heat ;  but  it  can  easily 
be  removed  when  necessary.  The  natural  expansion  of  the 
vessels  is  accommodated  by  the  water  pressure  in  the  hydraulic 
lifts  on  which  the  pots  stand.  When  the  lift  is  lowered  and 
sinks  with  the  lower  part  of  the  crucible  to  the  floor  level,  a 
large  pair  of  tongs  mounted  on  wheels  is  run  up,  and  catching 

Fig.  19, 


hold  of  the  crucible  by  two  projections  on  its  sides,  it  is  carried 
away  by  two  men  to  the  dumping  pits,  on  the  edge  of  which  it 
is  turned  on  its  side,  the  liquid  carbonate  of  soda  and  finely- 
divided  iron  which  form  the  residue  are  turned  out,  and  the 
inside  is  scraped  clean  from  the  opposite  side  of  the  pit,  under 
the  protection  of  iron  .shields.  When  clean  inside  and  out,  it 
is  lifted  again  by  the  truck  and  carried  back  to  the  furnace,  re- 
ceiving a  fresh  charge  on  its  way.  It  is  then  put  on  the  plat- 
form and  lifted  into  place,  having  still  retained  a  good  red  heat. 
It  takes  only  i)^  to  2  minutes  to  remove  and  empty  a  crucible. 


and  only  6  to  8  minutes  to  draw,  empty,  recharge,  and  replace 
the  five  crucibles  in  each  furnace.  The  time  occupied  in  re- 
ducing a  charge  is  one  hour  and  ten  minutes.  It  is  thus  seen 
that  one  bank  of  crucibles  yields  500  pounds  of  sodium  in 
twenty- four  hours,  the  battery  of  four  furnaces  producing  about 
a  ton  in  that  time. 

The  shape  of  the  condenser  has  been  altogether  changed. 
Instead  of  the  flat  form  used  on  the  furnace  at  London  (see 
Fig.  18),  which  resembled  the  condenser  used  in  the  Deville 
process,  a  peculiar  pattern  is  used  which  is  quite  different.  It 
consists  in  a  tube-shaped  cast-iron  vessel  S  inches  in  diameter, 
nearly  3  feet  long  over  all,  and  having  a  slight  bend  upwards  at 
a  point  about  20  inches  from  the  end.  At  this  bend  is  a  small 
opening  in  the  bottom,  which  can  be  kept  closed  by  a  rod  drop- 
ping into  it;  this  rod,  passing  through  a  tight- fitting  hole 
above,  can  be  raised  or  lowered  from  outside.  Thus  the 
sodium  can  either  run  out  continually  into  small  pots  placed 
beneath  the  opening  or  can  be  allowed  to  collect  in  the  con- 
denser until  several  pounds  are  present,  then  a  small  potful  run 
out  at  once,  by  simply  lifting  the  iron  rod.  The  outer  end  of 
the  condenser  is  provided  with  a  lid,  hinged  above,  which  can 
be  thrown  back  out  of  the  way  when  required.  This  lid  also 
contains  a  small  peep-hole  covered  with  mica.  In  the  top  of 
the  condenser  just  before  the  end  is  a  small  hole  through 
which  the  hydrogen  aud  carbonic  oxide  gases  escape  when  the 
end  is  closed,  burning  with  the  yellow  sodium  flame.  The 
bend  in  the  condenser  is  not  acute  enough  to  prevent  a  bar  be- 
ing thrust  through  the  end  right  into  the  outlet  tube  projecting 
from  the  furnace,  thus  allowing  the  whole  passage  to  be  cleaned 
out  should  it  become  choked  up.  Previous  to  drawing  the 
crucibles  from  the  furnace  for  the  purpose  of  emptying  them 
and  recharging,  the  small  pots  containing  the  metal  distilled 
from  one  charge  are  removed  and  empty  ones  put  in  their 
place.  Those  removed  each  contain  on  an  average  about  6  lbs. 
of  sodium,  or  30  lbs.  from  the  whole  furnace.  When  sufficiently 
cool,  petroleum  is  poured  on  top  of  the  metal  in  the  pots,  and 


they  are  -vvheeled  on  a  truck  to  the  sodium  casting  shop,  where 
the  sodium  is  melted  in  large  pots  heated  by  oil  baths  and  cast 
either  into  large  bars  ready  to  be  used  for  making  aluminium 
or  into  smaller  sticks  to  be  sold.  The  sodium  is  preserved 
under  an  oil  such  as  petroleum,  which  does  not  contain  oxygen 
in  its  composition,  and  the  greatest,  care  is  taken  to  protect  it 
from  water. 

Special  care  is  taken  to  keep  the  temperature  of  the  furnace 
at  about  iOOO°  C,  and  the  gas  and  air-valves  are  carefully  re- 
gulated so  as  to  maintain  as  even  a  temperature  as  possible. 
The  covers  remain  in  the  furnace  from  Sunday  night  to  Satur- 
day afternoon,  and  the  crucibles  are  kept  in  use  till  worn  out, 
when  new  ones,  previously  heated  red-hot,  are  substituted 
without  interrupting  the  general  running  of  the  furnace.  These 
bottom  halves  of  the  crucibles  are  the  only  part  of  the  plant 
liable  to  exceptional  wear  and  tear,  and  their  durability  is  found 
to  depend  very  much  on  the  soundness  of  the  casting,  because 
any  pores  or  defects  are  rapidly  eaten  into  and  the  pot  de- 
stroyed. The  average  duration  of  each  crucible  is  now  750 
lbs.  of  sodium,  or  125  charges. 

Apropos  of  the  reaction  involved  in  the  reduction,  it  has 
probably  been  observed  that  Mr.  MacTear  proposes  a  different 
formula  from  that  suggested  by  Mr.  Castner.  Mr.  Weldon  re- 
marked that  when  a  mixture  of  sodium  carbonate  and  carbon 
was  heated  the  carbon  did  not  directly  reduce  the  soda,  but  at 
a  high  temperature  the  mixture  gives  off  vapors  of  oxide  of 
sodium  (Na^O)  part  of  which  dissociates  into  free  oxygen  and 
sodium  vapor;  as  soon  as  this  dissociation  takes  place  the 
carbon  takes  up  the  oxygen,  forming  carbonic  oxide,  and  thus, 
by  preventing  the  recombination  of  the  sodium  and  oxygen, 
leaves  free  sodium  vapors. 

Dr.  Kosman,  speaking  in  "  Stahl  und  Eisen,"  January,  1889, 
on  Castner's  process,  gives  the  following  explanation  of  the  re- 
actions taking  place : — 

Ten  kilos  of  caustic  soda  and  5  kilos  of  carbide  (containing 
1.5  kilos  of  carbon)  give  the  following  reaction: 


4NaOH  +  FeCj  =  Na^COs  +  Fe  +  4H  +  CO  +  2Na, 

and  half  the  sodium  in  the  mixture  is  obtained. 

Ten  kilos  of  caustic  soda  and  10  kilos  of  carbide  (containing 
3  kilos  of  carbon)  give  this  reaction — 

zNaOH  +  FeQ  =  NaCO  +  Fe  +  2H  +  CO  +  Na, 

and  half  the  sodium  in  the  mixture  is  again  obtained. 

If  20  kilos  of  caustic  soda  and  15  kilos  of  carbide  are  mixed, 
both  the  above  reactions  take  place ;  but  if  the  ignition  is  con- 
tinued, the  sodium  carboxyd  (NaCO)  reacts  on  the  sodium 
carbonate  according  to  the  reaction — 

Na^COs  +  NaCO  =  sNa  +  2CO2, 

and  the  entire  reaction  may  be  represented  by 

sNaOH  +  FeC^  =  sNa  +  Fe  +  3 H  +  CO  -h  CO,, 

and  all  the  sodium  in  the  mixture  is  obtained. 

This  is  the  reaction  first  proposed  by  Mr.  Castner  (see  p. 
206),  and  the  proportions  indicated  by  it  gave  him  the  largest 
return  of  sodium.  Mr.  MacTear,  however,  states  that  the  re- 
action which  takes  place  is  conditioned  largely  by  the  tempera- 
ture, and  that  at  1000°  C.  it  is  probably  to  be  represented  by 

6NaOH  -I-  FeCj  =  2Na2C03  +  6H  -F  Fe  +  zNa, 

which  is  essentially  the  same  as  that  given  by  Sir  Henry  Ros- 
coe  in  his  discourse,  viz  : — 

3NaOH  +  C  =  Na.CO,  +  3H.  +  Na. 

This  reaction  would  require  18^  lbs.  of  carbide  to  50  lbs.  of 
caustic  soda,  and  since  the  sodium  carbonate  is  easily  converted 
back  into  caustic  by  treatment  with  lime,  the  production  of  so 
much  carbonate  is  offset  by  the  ease  with  which  the  reaction 
takes  place,  and  the  added  advantage  that  the  gas  evolved  with 
the  sodium  is  solely  hydrogen,  thus  allowing  the  reduction  to 


proceed  in  an  atmosphere  of  that  gas,  and  reducing  the  pro- 
duction of  the  usual  deleterious  sodium  carbides  to  a  minimum. 
A  further  discussion  of  this  subject  will  come  up  in  consider- 
ing Netto's  process. 

Netto's  Process  (1887). 
Dr.  Curt  Netto,  of  Dresden,  took  out  patents  in  several 
Eurupean  countries,*  which  were  transferred  to  and  operated 
by  the  AlHance  Aluminium  Company,  of  London  (see  p.  31). 
The  process  is  continuous,  and  is  based  on  the  partial  reduc- 
tion of  caustic  soda  by  carbon.  Dr.  Netto  observes  that  car- 
bon will  reduce  caustic  soda  at  first  at  a  red  heat,  but  a  white 
heat  is  necessary  to  finish  the  reduction,  the  explanation  being 
that  the  reaction  is  at  first — 

4NaOH  +  C  =  Na^COa-l-  2H,  -t-  CO  +  Na„ 

and  that  the  carbonate  is  only  reduced  at  a  white  heat.  To 
avoid  any  high  temperature,  the  first  reaction  only  is  made  use 
of,  the  carbonate  being  removed  and  fresh  caustic  supplied 
continuously,  and  without  interrupting  the  operation  or  admit- 
ting air  into  the  retort  in  which  the  reduction  takes  place. 

A  vertical  cast-iron  retort,  protected  by  fire-clay  coating,  is 
surrounded  by  flues.  The  flame  after  heating  the  retort  passes 
under  an  iron  pot  in  which  the  caustic  soda  is  kept  melted,  and 
situated  just  above  the  top  of  the  retort.  This  pot  has  an  out- 
let tube  controlled  by  a  stop-cock,  by  which  the  caustic  may 
be  discharged  into  a  funnel  with  syphon-shaped  stem  fastened 
into  the  top  of  the  retort.  There  is  also  a  syphon-shaped  out- 
let at  the  bottom  of  the  retort,  through  which  the  molten  so- 
dium carbonate  and  bits  of  carbon  pass.  A  hole  with  tight  lid 
in  the  upper  cover  is  provided  for  charging  charcoal.  A  tube 
passes  out  just  beneath  the  upper  cover,  connecting  with  a 
large  condenser  of  the  shape  used  by  Deville  (see  Fig.  20). 
In  operating,  the  retort  is  heated  to  bright  redness,  filled  one- 
third  with  best  wood  charcoal,  and  then .  molten  caustic  soda 

♦German  patent  (D.  R.  P.)  45105;  English  patent,  October  26,  1887,  No.  14602. 



tapped  from  the  melting-pot  into  the  funnel,  the  feed  being  so 
regulated  that  the  funnel  is  kept  full  and  the  retort  closed. 
The  lower  opening  is  kept  closed  until  enough  sodium  carbon- 
ate has  accumulated  to  lock  the  syphon  passage  air  tight. 
When  after  several  hours'  working  the  charcoal  is  almost  all 
used  up,  the  supply  of  caustic  soda  is  shut  off  for  a  time  and 

Fig.  20. 

the  retort  recharged  through  the  opening  in  the  upper  lid, 
when  the  operation  goes  on  as  before.  The  sodium  carbonate 
produced  is  easily  purified  from  carbon  by  solution.  Since 
sodium  vapor  at  a  high  temperature  is  very  corrosive,  all  rivets 
and  screw  joints  must  be  avoided  in  making  the  retort.  On 
this  account,  the  outlet  tubes  should  be  cast  in  one  piece  with 
the  retort. 


Both  Netto's  process  and  Castner's  were  in  use  for  a  con- 
siderable time  ( 1 888-1 891),  and  produced  sodium  in  large 
quantities  and  cheaply.  With  the  advent  of  the  cheaper  elec- 
trolytic methods  of  producing  aluminium,  the  sodium  methods 
were  put  to  a  sharp  struggle  for  existence.  The  Alliance  Alu- 
minium Company,  working  the  Netto  process,  soon  gave  up 
the  fight.  The  Aluminium  Company,  Limited,  working  Cast- 
ner's process,  were  enabled  to  continue  making  aluminium  for 
some  time  longer  by  an  invention  of  Mr.  Castner's  to  produce 
sodium  electrolytically.  This  process  is  still  being  used,  but 
the  sodium  produced  is  used  for  various  other  purposes  than 
making  aluminium,  the  extraordinary  cheapness  of  the  electro- 
lytic processes  rendering  competition  impossible. 

Reduction  of  Sodium  Compounds  by  Electricity. 

The  decomposition  of  fused  sodium  chloride  by  the  electric 
current  seems  to  promise  the  economic  production  of  sodium, 
for  not  only  is  this  metal  formed,  but  chlorine  is  obtained  as  a 
by-product,  its  value  reducing  very  much  the  cost  of  the 

P.  JablochofF  has  devised  the  following  apparatus  for  decom- 
posing sodium  or  potassium  chlorides.*     (Fig  21.) 

The  arrangement  is  easily  understood.  The  salt  to  be  de- 
composed is  fed  in  by  the  funnel  into  the  kettle  heated  by  a  fire 
beneath.  The  positive  pole  evolves  chlorine  gas,  and  the 
negative  pole  evolves  vapor  of  the  metal,  for,  as  the  salt  is 
melted,  the  heat  is  sufficient  to  vaporize  the  metal  liberated. 
The  gas  escapes  through  one  tube  and  the  metallic  vapor  by 
the  other.     The  vapor  is  led  into  a  condenser  and  solidified. 

Prof.  A.  J.  Rogers,  of  Milwaukee,  Wis.,  has  made  a  number 
of  attempts  to  reduce  sodium  compounds  electrolytically,  using 
as  a  cathode  a  bath  of  molten  lead  and  producing  an  alloy  of 
lead  and  sodium  which  he  makes  use  of  for  the  reduction  of 
aluminium  compounds.     Although  these  attempts  are  hardly 

*  Mierzinski. 



past  the  experimental  stage,  yet  the  record  of  the  results  ob- 
tained may  very  probably  be  interesting  and  valuable  to  other 
investigators  in  this  line. 

Prof.  Rogers  reasons  that  from  the  known  heat  of  combina- 

FlG.  21. 

unvrm  |>T«" 

tion  of  sodium  and  chlorine  (4247  calories  per  kilo  of  sodium) 
there  is  enough  potential  energy  in  a  pound  of  coal  to  separate 
nearly  two  pounds  of  sodium,  if  any  mode  of  applying  the  com- 
bustion of  the  coal  to  this  end  without  loss  could  be  devised. 
If,  however,  this  energy  is  converted  into  mechanical  work,  this 
again  into  electrical  energy,  and  this  latter  used  to  decompose 
sodium  chloride,  we  can  easily  compute  the  amount  of  coal  to 
be  used  in  a  steam  boiler  to  produce  a  given  amount  of  sodium 
by  electrolysis.  Now,  if  the  electric  current  could  be  applied 
without  loss  in  decomposing  sodium  chloride,  i  electric  horse- 
power (746  Watts)  would  produce  about  8  lbs.  of  sodium  in 
24  hours.  But  as  in  practice  one  mechanical  horse-power  ap- 
plied to  a  dynamo  yields  only  80  or  90  per  cent,  of  an  electric 
horse-power,  and  as  about  4  lbs.  of  coal  are  used  per  indicated 


horse-power  per  hour,  from  105  to  120  lbs.  of  coal  would  be 
required  per  day  to  produce  this  result,  or  about  15  lbs.  per  lb. 
of  sodium.  Since,  however,  there  is  a  transfer  resistance  in  the 
passage  of  the  electric  current  through  the  molten  electrolyte, 
more  than  this  will  be  required,  in  proportion  to  the  amount  of 
current  thus  absorbed. 

The  temperature  of  fusion  of  sodium  chloride  is  given  by 
Carnelly  as  Tj6°  C,  but  Prof.  Rogers  remarks  that  the  fusing 
point  may  be  lowered  considerably  by  the  presence  of  other 
salts ;  for  instance,  it  melts  about  200°  lower  if  a  small  amount 
of  calcium  chloride  or  potassium  chloride  is  present.  We  will 
quote  the  results  of  some  experiments  as  given  by  Prof. 

"The  following  results  were  obtained  among  many  others  by 
using  a  Grove  battery,  a  Battersea  crucible  to  hold  the  sodium 
chloride,  a  carbon  anode  and  an  iron  cathode  terminating  in  a 
tube  of  lime  placed  in  the  melted  salt.  As  soon  as  metallic 
sodium  escaped  and  burnt  at  the  surface  of  the  liquid  the  cur- 
rent was  stopped.  A  little  sodium  was  oxidized,  but  a  consid- 
erable amount  was  found  in  the  tube  in  the  metallic  state.  In 
six  experiments  the  amount  of  sodium  obtained  was  from  50  to 
85  per  cent,  of  the  theoretical  amount,  averaging  65  per  cent. 
It  thus  seemed  that,  with  suitable  apparatus,  from  5  to  6  lbs.  of 
sodium  could  be  obtained  in  24  hours  per  electric  horse-power. 
Thus,  if  there  were  no  practical  difficulties  in  the  construction 
of  the  crucibles  and  other  apparatus  involved,  nor  in  working 
continuously  on  a  large  scale,  the  metal  could  be  obtained  at 
small  cost.  Various  forms  of  crucibles  were  used  and  attempts 
made  to  distil  the  metal  when  formed  at  the  negative  electrode 
(sodium  volatilizing  at  about  900°  C),  but  the  sodium  vapor 
carries  with  it  a  large  amount  of  sodium  chloride  as  vapor,  and 
the  distillation  is  attended  with  difficulty. 

"  During  the  last  three  years  I  have  experimented  on  the 
reduction  of  sodium  chloride,  using  molten  negative  electrodes 
and  especially  lead.  Lead,  tin,  zinc,  cadmium  and  antimony 
*  Proceedings  of  the  Wisconsin  Natural  History  Society,  April,  1889. 


all  readily  .alloy,  with  sodium,  a  large  part  of  which  can  be  re- 
covered from  the  alloys  by  distillation  in  an  iron  crucible.  They 
can  be  heated  to  a  higher  temperature  than  pure  sodium  in 
acid  crucibles  without  the  sodium  attacking  the  crucible.  In 
the  following  experiments  a  dynamo  machine  was  used  to  sup- 
ply the  current. 

"Experiment  i.  A  current  averaging  72  amperes  and  33 
volts  was  passed  through  molten  sodium  chloride  contained  in 
two  crucibles  arranged  in  series,  for  two  hours.  Each  con- 
tained 30  lbs.  of  salt;  in  the  first  was  put  104  grammes  of  tin, 
in  the  second  470  grammes  of  lead,  each  serving  as  cathode, 
and  connection  being  made  through  the  bottom  of  the  crucible. 
A  carbon  anode  passed  through  the  cover  and  extended  to 
within  three  inches  of  the  molten  cathode.  The  crucible  con- 
taining the  tin  was  nearer  the  fire  and  consequently  hotter,  and 
had  an  average  potential  across  the  electrodes  of  12  volts, 
while  that  containing  the  lead  cathode  was  21  volts.  When  at 
the  end  of  two  hours  the  carbons  were  removed  and  the  cru- 
cibles cooled  and  broken  open,  the  lead  alloy  was  found  to 
contain  96  grammes  of  sodium,  or  17  per  cent.  There  was 
about  90  grammes  of  sodium  found  in  the  tin  alloy,  or  between 
45  and  50  per  cent.  Both  these  alloys  rapidly  oxidized  in  the 
air,  and  when  thrown  into  water  the  action  was  very  energetic, 
in  the  case  of  the  tin  alloy  the  liberated  hydrogen  being  ignited, 
and  after  the  reaction  the  metals  were  found  at  the  bottom  of 
the  vessel  in  a  finely  divided  state.  Both  these  alloys  reduce 
cryolite  or  aluminium  chloride." 

In  Prof.  Rogers'  further  experiments  cryoHte  was  added  to 
the  bath,  so  that  sodium  was  produced  and  aluminium  formed 
in  one  operation.  (See  under  "Electrolytic  Processes," 
Chap.  XI.) 

L.  Grabau,  of  the  "  Aluminium  Werke  zu  Trotha,"  has 
made  the  following  observations  on  the  electrolysis  of  molten 
sodium  chloride.  When  the  melted,  salt  is  subjected  to  the 
electric  current,  the  resistance  of  the  bath  quickly  rises  and  it 
becomes  almost  inipossible  to  force  the  current  through,     This 


is  probably  due  to  the  formation  of  a  non-conducting  sub- 
chloride.  The  formation  of  this  salt  can  be  prevented  by  the 
addition  of  some  potassium  chloride  and  the  chloride  of  an 
alkaHne-earth  metal  to  the  bath.  In  his  patents,*  Grabau 
recommends  the  use  of  a  mixture  of  sodium,  potassium  and 
strontium  chlorides,  in  the  proportion  of  88  sodium  chloride, 
112  potassium  chloride,  and  159  strontium  chloride.  With  this 
mixture,  Grabau  claims  to  obtain  almost  pure  sodium,  contain- 
ing only  about  3  per  cent,  of  potassium  and  no  trace  of 
strontium,  while  at  the  same  time  95  per  cent,  of  the  metal 
which  the  current  should  theoretically  give  is  obtained.  For 
all  the  purposes  to  which  sodium  is  now  applied  the  presence  of 
the  potassium  is  not  in  the  least  prejudicial.  Borchers  sub- 
stantiates the  fact  that  from  a  mixture  of  potassium  and  sodium 
chlorides,  which  is  very  fluid,  only  sodium  is  liberated  by  the 
current  if  it  is  not  too  strong  and  if  the  sodium  chloride  de- 
composed is  at  once  replaced.  For  carrying  on  his  process, 
Grabau  uses  the  apparatus  shown  in  Fig.  22.  The  positive 
poles  are  carbon  rods  (C),  the  negative  an  iron  pipe  E,  slit  in 
its  lower  part  and  surrounded  by  a  bell-shaped  porcelain  cover 
B.  As  the  molten  sodium  is  lighter  than  the  bath  material,  it 
rises  into  the  pipe  £  and  passes  away  through  the  branch  a  into 
a  condenser  where  it  collects  under  petroleum.  The  screw  H 
can  be  turned  downwards  to  clean  out  the  tube  E  in  case  it 
stops  up.  It  is  intended  that  the  vessel  should  be  heated  by 
hot  gases  passing  through  the  flues  G  G,  and  its  temperature  so 
regulated  that  the  sodium  passes  off  in  the  liquid  state.  The 
chlorine  generated  passes  off  by  the  tube  d.  In  order  to  pre- 
vent the  corrosion  of  the  cover  B,  Grabau  has  even  con- 
structed an  apparatus  in  which  it  contained  an  iron  lining  and 
was  water-cooled. 

The  method  now  used  by  Castner  .consists  in  electrolyzing 
molten  caustic  soda  at  the  lowest  possible  temperature.  Pure 
caustic  soda  melts  below  redness,  and  if  kept  at  a  temperature 

♦German  Patents  (D.  R.  P.)  Nos.  51898  and  56230  (1890). 



not  more  than  20°  above  its  melting  point  (310°  C),  it  can  be 
easily  and  continuously  electrolyzed.  Arrangements  must 
therefore  be  provided  for  keeping  the  temperature  of  the  bath 
very  constant,  and  for  removing  the  sodium  quickly  from  the 
bath  in  order  to  prevent  loss  by  corrosion.  The  apparatus 
consists  of   an  iron  crucible,  embedded  in  brickwork,  in  which 

Fig.  22. 

the  caustic  soda  is  melted  by  the  heat  of  a  circular  gas  burner 
surrounding  the  pot  (Fig.  23).  The  negative  electrode  passes 
up  through  the  bottom  of  the  pot,  the  space  between  it  and  the 
sides  of  the  hole  being  allowed  to  fill  up  with  solid  caustic.  A 
tubular  sleeve  of  iron  descends  from  the  cover  and  envelopes 
the  top  of  this  electrode.  Outside  of  this  are  the  positive  elec- 
trodes.    An  opening  is  provided  in  the  cover  for  the  escape  of 



gas  and  introduction  of  a  thermometer.  In  operation,  the  heat 
caused  by  the  passage  of  the  current  is  sufificient  to  keep  the 
bath  melted.     The  free  sodium  floats  on  the  surface  of  the  bath 

inside  the  iron  sleeve   surrounding  the  negative  electrode,  and 
is  skimmed  off  with  a  small  ladle  having  fine  perforations.    The 
operation  is  continuous,  and  afifords  sodium  at  a  cost  probably 
not  greater  than  15  cents  per  pound. 



The  branch  of  chemical  science  called  thermal  chemistry  may 
be  said  to  be  yet  in  its  infancy.  Although  an  immense  mass 
of  thermal  data  has  been  accumulated,  yet  the  era  of  great 
generalizations  in  this  subject  has  not  yet  been  reached ;  and 
although  we  know  with  a  fair  degree  of  accuracy  the  heat  of 
combination  of  thousands  of  chemical  compounds,  including 
nearly  all  the  common  ones,  yet  the  proper  way  to  use  these 
data  in  predicting  the  possibility  of  any  proposed  reaction  re- 
mains almost  unknown.  The  principal  barriers  in  the  way  are 
two:  1st,  the  unknown  quantities  entering  into  almost  every 
chemical  reaetion  thermally  considered,  i.  e.,  the  heat  of  com- 
bination of  elementary  atoms  to  form  molecules  of  the  ele- 
ments ;  2d,  the  uncertainty  as  regards  the  critical  temperature 
at  which  a  given  exchange  of  atoms  and  consequent  reaction 
will  take  place.  We  will  explain  what  is  meant  by  these  state- 

To  illustrate,  let  us  consider  the  case  of  hydrogen  uniting 
with  oxygen  to  form  water  according  to  the  formula — 

2(H— H)  -I-  (0=  0)=  2H,0 

where  (H — H)  and  (O  ^  O)  represent  respectively  molecules 
of  hydrogen  and  oxygen.  Now,  as  i  kilo  of  hydrogen  unites 
with  8  of  oxygen  to  form  9  of  water,  setting  free  34,462  units 
of  heat  (calories),  if  we  take  the  atomic  weights  in  the  above 
reaction  as  representing  kilos,  we  shall  have  the  thermal  value 
of  the  reaction  4  X  34,462  = -|- 137,848  calories.  But  this' 
quantity  is  evidently  the  algebraic  sum  of  the  heat  evolved  in 



the  union  of  4  kilos  of  hydrogen  atoms  with  32  kilos  of  oxygen 
atoms,  and  the  heat  absorbed  in  decomposing  4  kilos  of  hydro- 
gen gas  into  atoms!  and  32  kilos  of  oxygen  gas  into  atoms. 
These  two  latter  quantities  are  unknown,  though  a  few  chem- 
ists have  concluded  from  studies  on  this  question  that  they  are 
probably  very  large.     It  has  been   calculated   that  the  reaction 

H  -|-  H  =  (H — H)  sets  free  240,000  calories, 
and  0  4-0^  (O  =  O)  sets  free  147,200  calories ; 

If  these  numbers  are  approximately  true,  then 

4H  +  20^  2H2O  would  set  free  about  773,000  calories. 

If  these  quantities  are  really  anything  like  so  large,  and  if 
they  are  at  sometime  determined  with  precision,  thermo-chem- 
ical  principles  and  conclusions  will  be  greatly  modified.  Mean- 
while, predictions  based  on  the  data  we  have,  lose  all  possibility 
of  certainty,  and  so  we  need  to  keep  in  mind  in  our  further 
discussion  that  our  deductions  at  the  best  are  only  probabil- 
ities. Further,  suppose  that  we  mix  i  kilo  of  hydrogen  gas 
and  8  kilos  of  oxygen  gas,  put  them  in  a  tight  vessel  and  keep 
them  at  the  ordinary  temperature.  No  reaction  will  take  place 
in  any  length  of  time,  even  though  34,462  calories  would  be 
set  free  thereby.  The  explanation  of  this  is  that  the  atoms  of 
hydrogen  and  oxygen  are  so  firmly  bound  to  each  other  in  the 
molecules,  that  the  dissimilar  atoms  have  not  strength  of  afiSnity 
sufiScient  to  break  away  in  order  to  combine.  It  is  well  known 
that  a  spark  only  is  necessary  to  cause  an  explosive  combina- 
tion of  the  gases  under  the  above  conditions,  the  temperature 
of  the  spark  expanding  the  gases  coming  in  contact  with  it, 
causing  the  atoms  to  swing  with  more  freedom  in  the  molecules ; 
and  as  soon  as  two  atoms  of  hydrogen  come  within  the  .sphere 
of  attraction  of  an  atom  of  oxygen  and  form  a  molecule  of 
water,  the  heat  liberated  is  immediately  communicated  to  the 
adjacent  atoms,  and  almost  instantaneously  the  entire  gases 
have  combined.     The  same  principle  undoubtedly  holds  true 


in  cases  of  reduction.  Carbon  may  be  mixed  with  litharge 
and  the  mixture  left  in  the  cold  forever  without  reacting,  but  at 
a  certain  temperature  the  carbon  will  abstract  the  oxygen.  The 
temperatures  at  which  reactions  of  this  nature  will  take  place 
are  often  determined  experimentally. 

There  are  other  points  which  are  somewhat  indeterminate  in 
these  discussions,  such  as  the  influence  of  the  relative  masses 
of  the  reacting  bodies,  their  physical  states,  i.  e.,  solid,  liquid 
or  gaseous,  also  the  influence  of  the  physical  conditions  favor- 
ing the  formation  of  a  certain  compound ;  but  the  nature  of  the 
subject  and  the  meagreness  of  data  in  the  particular  pheno- 
menon of  reduction,  render  it  inexpedient  if  not  impracticable 
to  take  these  points  into  consideration. 

Starting  with  the  above  remarks  in  view,  we  will  consider  the 
heat  generated  by  the  combination  of  aluminium  with  certain 
other  elements,  as  has  been  determined  experimentally,  and 
study,  from  a  comparison  with  the  corresponding  thermal  data 
for  other  elements,  what  possibilities  are  shown  for  reducing 
these  aluminium  compounds. 

The  heat  generated  by  the  combination  of  aluminium  with 
the  different  elements  is  given  as  follows :  the  first  column  giv- 
ing the  heat  developed  by  54  kilos  of  aluminium  (representing 
AI2),  and  the  second  the  heat  per  atomic  weight  of  the  other 
element,  e.  g.,  per  16  kilos  of  oxygen. 

Element.                 Compound.  Calories.  Calorie.s.  Authority. 

Oxygen *  Al^Oj  391,600  130,500  Berthelot. 

392,600  130,900  Bailie  &  F^ry. 

Fluorine 2AIF3  552,000  92,000  Berthelot. 

Chlorine 2AICI3  321,960  53,66o  Thomsen. 

Bromine 2AlBr3  239,440  39,900                " 

Iodine 2AU3  140,780  23,460                " 

Sulphur AI2S3  124,400  41,467  Sabatier. 

*  Berthelot's  number  represented  the  formation  of  the  hydrated  oxide,  AIJO3.3H2O, 
and,  for  want  of  knowing  the  heat  of  hydration,  has  been  generally  used  as  the  heat 
of  formation  of  AljOj.  Recently,  J.  B.  Bailie  and  C.  F4ry  (Ann.  de  Chim.  et  de 
Phys.,  June,  1889,  p.  250)  have,  by  oxidizing  aluminium  amalgam,  obtained  the  above 
figure  for  the  heat  of  formation  of  AI2O3,  and  determined  that  the  beat  of  hydration 
is  3000  calories,  which  would  make  the  heat  of  formation  of  the  hydrated  oxide 


Let  US  consider  the  theoretical  aspect  of  the  reduction  of 
alumina.  The  heat  given  out  by  other  elements  or  com- 
pounds which  unite  energetically  with  oxygen  is  as  follows,  the 
quantity  given  being  that  developed  by  combination  with  16 
kilos  (representing  one  atomic  weight)  of  oxygen. 

Element.  Compound.  Calories. 

AlTiminlum AljOj        130,500 

Sodium Na.p  99, 760 

Potassium Kfi  100,000  ( ?) 

Barium BaO  124,240 

Strontium SrO  1 28,440 

Calcium CaO  130,930 

Magnesium MgO  145,860 

Manganese MnO  95,ooo  ( ?) 

Silicon SiOj  1 10,000 

Zinc ZnO  85,430 

Iron FejOj  63,700 

Lead PbO  50,300 

Copper CuO  37>i6o 

"      CU2O  40,810 

Sulphur SO2  35.540 

Hydrogen H^O  68,360 

Carbon CO  29,000 

"       COj  48,480 

Carbonic  anhydride CO^  67,960 

Potassium  cyanide KCyO  72,000 

On  inspecting  this  list  we  find  magnesium  to  be  the  only  metal 
surpassing  aluminium,  while  calcium  is  about  the  same.  This 
would  indicate  that  the  reaction 

AlA  +  3Mg  =  Al,  +  3MgO 

would,  if  it  were  possible  to  bring  the  alumina  and  magnesium 
in  the  proper  conditions  for  reacting,  develop  about 

(145,860 — 130,500)  X  3  =  46,080  calories, 

and  points  to  the  possibility  of  reducing  alumina  by  nascent, 
molten,  or  vaporized  magnesium,  under  certain  conditions.  In 
fact,  since  this  paragraph  was  first  written,  in  1890,  Dr.  Clemens 
Winkler  has  succeeded  in  performing  the  reduction  in  part.* 

*  Berliner  Berichte,  1890,  p.  772. 


He  found  that  when  alumina  was  heated  with  magnesium  pow- 
der in  a  current  of  hydrogen,  a  nearly  black  powder  resulted, 
containing  a  lower  oxide  of  aluminium,  AlO,  the  reaction 

2AI2O,  +  Mg  =  MgO.AljO,  +  2AIO  ; 

the  magnesia  formed  uniting  with  alumina  to  form  an  alum- 

We  notice  further  the  fact  that  sodium  or  potassium  could 
not  reduce  alumina  without  heat  being  absorbed  in  large 
quantity,  and  it  is  interesting  to  remember  that  some  of  the 
first  attempts  at  isolating  aluminium  by  using  potassium  were 
made  on  alumina,  and  were  unsuccessful,  so  that  it  is  practi- 
cally acknowledged  that  while  these  metals  easily  reduce  other 
aluminium  compounds  (according  to  reactions  which  are  ther- 
mally possible,  as  we  shall  see  later  on)  yet  they  cannot  reduce 
alumina,  under  any  conditions  so  far  tried. 

When  we  consider  the  case  of  reduction  by  the  ordinary  re- 
ducing agents,  hydrogen,  carbon,  or  potassium  cyanide,  we  are 
confronted  in  every  case  with  large  negative  quantities  of  heat, 
i.  e.,  deficits  of  heat.  So  large  do  these  quantities  appear  that 
it  is  very  small  wonder  that  the  impossibility  of  these  reduc- 
tions occurring  under  any  conditions  has  been  strongly  affirmed, 
For  instance 


would  require 

(130,500 — 68,360)  X  3     =  186,420  calories. 

AI2O3       +  3C        =Alj  -I-3CO  304,500  calories. 

AI2O3        +  i>^C     =  AI2  -h  ii^COa  246,060  calories. 

Al,03       -I- 3KCy   =  Al,  +  3KCyO  175,500  calories. 

AlA       +3CO      =h\  +  7,C0,  187,620  calories. 

The  above  quantities  represent  the  differences  between  the 
heats  of  formation  of  alumina  and  the  product  of  the  reduc- 
tion, assuming  the  reaction  to  take  place  at  ordinary  temper- 
atures.    At  high  temperatures  these  heats  of  formation  are  in 


general  less  than  they  would  be  at  low  heats,  and  if  the  heat  of 
formation  of  alumina  decreases  faster  than  .the  heat  of  combi- 
nation of  the  reducing  agent  with  oxygen,  the  dififerences  noted 
above  would  be  less  and  the  reaction  easier  to  produce.  This 
must  be  what  actually  takes  place.  For  instance,  at  the  heat 
of  an  electric  furnace,  say  2500°  to  3000°C.,  molten  alumina 
is  reduced  by  carbon  present  in  large  quantity,  that  is,  the  dif- 
ference beiween  the  heats  of  formation  of  AI2O3  and  3 CO  has 
become  so  small  that  the  reaction  takes  place.  Similarly, 
Warren  has  recently  reduced  alumina  by  heating  it  in  a  lime 
tube  by  an  oxy-hydrogen  blow-pipe,  passing  hydrogen  through 
the  tube.  We  here  have  a  reaction  which  is  negative  by  186,- 
000  calories  at  ordinary  temperatures,  taking  place  at  a  tem- 
perature probably  not  over  2000°C. 

The  conditions  which  render  the  carrying  out  of  these  diffi- 
cult reductions  possible  are  therefore  : 

1 .  A  high  temperature,  which  weakens  the  heat  of  formation 
of  alumina. 

2.  An  excess  of  the  reducing  agent,  which  is  thus  assisted 
simply  by  the  overpowering  influence  of  its  mass. 

3.  Fluidity  of  the  substance  to  be  reduced. 

4.  Intimate  contact  with  the  reducing  agent. 

5.  Favorable  conditions  for  the  formation  and  removal  of  the 
gaseous  products  of  the  reduction. 

Concerning  these,  I  would  remark  that  the  fluidity  of  the  sub- 
stance to  be  reduced  may  be  attained  by  other  means  than  a 
high  temperature.  The  alumina  may,  for  instance,  be  liquefied 
by  solution  in  a  bath  of  molten  cryolite.  If  we  dissolve  it  in 
molten  caustic  soda  we  get  a  combination  of  alumina  and  soda 
which  will  remain  fluid  if  too  much  alumina  is  not  added. 
Such  fluidity  also  allows  much  more  intimate  contact  with  the 
reducing  agent  if  it  is  a  solid.  .  If  the  reducing  agent  is  a  gas, 
most  intimate  contact  is  obtalined  by  finely  pulverizing  the  alu- 
mina. If  the  reducing  agent  is  a  solid  and  the  product  of  the 
reduction  would  be  a  gas,  its  formation  would  be  accel- 
erated by  reducing  the  pressure  in  the  apparatus.     In  other 



words,  a  partial  vacuum  would  undoubtedly  aid  in  bringing 
about  the  reduction,  and  would  help  to  keep  the  aluminium  in 
the  metallic  state  by  removing  quickly  the  product  of  reduction 
and  so  preventing  re-oxidation.  I  have  no  hesitation  in  affirm- 
ing that  since  we  now  know  that  carbon  does  reduce  molten 
alumina  below  3000°,  and  hydrogen  reduces  solid  alumina  at 
2000°,  the  application  of  correct  principles  by  intelligent  inves- 
tigators, with  properly  constructed  apparatus,  would  undoubt- 
edly result  in  discovering  methods  of  producing  the  same  reac- 
tions at  lower  temperatures  and  on  a  larger  scale.  Whether 
these  methods  of  producing  aluminium  could  compete  with  the 
present  electrolytic  ones  is  another  question,  but  it  is  certainly 
interesting  to  mark  the  possibility  of  processes  which  some 
future  investigator  may  bring  to  commercial  success. 

As  the  basis  of  our  discussion  of  the  reduction  of  aluminium 
chloride,  bromide,  or  iodide,  we  give  a  table  of  heat  developed 
by  the  combination  of  some  of  the  elements  with  one  atomic 
weight  (in  kilos)  of  each  of  these  haloids. 































f  5o,6oot 
1 48,600* 


]  40,640t 
I  37.500* 
























Potassium  . . 


Lithium .... 
Barium  .... 
Strontium  . . 
Calcium .... 
Manganese  . 



Mercury . . .  • 



Copper  . . . . 
Hydrogen.  . 


















f  30,coot 

■j  26,600 

(.  24,500 



— 6,000 

*Thomsen.  t  Andrews.  J  Jahresbericht  der  Chemie,  1878,  p.  102, 

On  inspecting  this  table  we  notice  that,  in  general,  all  the 


metals  down  to  zinc  develop  more  heat  in  forming  chlorides,  and 
very  probably  also  in  forming  bromides  and  iodides,  A  re- 
action, then,  between  aluminium  chloride  and  any  of  these 
metals,  forming  aluminium  and  a  chloride  of  the  metal,  would 
be  exothermic,  which  means,  generally  speaking,  that  if  alu- 
minium chloride  and  any  one  of  these  metals  were  heated  to- 
gether to  the  critical  point  at  which  the  reaction  could  begin, 
the  reaction  would  then  proceed  of  itself,  being  continued  by  the 
heat  given  out  by  the  first  portions  which  reacted.  Zinc  seems 
to  lie  on  the  border  line,  and  the  evidence  as  to  whether  zinc 
will  practically  reduce  these  aluminium  compounds  is  still  con- 
tradictory, as  may  be  seen  by  examining  the  paragraphs  under 
" Reduction  by  Zinc."     (Chap.  XII.) 

Of  the  first  six  metals  mentioned  in  the  table  after  aluminium, 
only  potassium  and  sodium  are  practically  available.  The  re- 

AlCl3  +  3K  =  AH-3KCl  develops  155,820  cal. 
AlCls-F  3Na  =  Al-f- 3NaCl  develops  132,090  cal. 

and  the  result  of  this  strong  disengagement  of  heat  is  seen 
when,  on  warming  these  ingredients  together,  the  reaction  once 
commenced  at  a  single  spot  all  external  heat  can  be  cut  off,  and 
the  resulting  fusion  will  become  almost  white  hot  with  the  heat 
developed.  In  fact,  the  heat  developed  in  the  second  reaction 
would  theoretically  be  sufficient  to  heat  the  aluminium  and 
sodium  chloride  produced  to  a  temperature  between  3000°  and 

Magnesia  should  act  in  a  similar  manner,  though  not  so  vio- 
lently, since 

2AlCl3  +  3Mg=Al2  +  3MgCl2  develops  131,000  cal. 

And  manganese  possibly  also,  since 

2AICI3  +  3Mn  =  Ala  -f-  3MnCl  develops  14,040  cal. 

The  reduction  of  aluminium  chloride,  bromide,  or  iodide  by 
hydrogen  is  thermally  strongly  negative,  which  would  indicate 
a  very  small  possibility  of  the  conditions  ever  being  arranged  so 


as  to  render  the  reaction  possible.     For  instance,  taking  the 
most  probable  case, 

AICI3  +  3H  =  Al  +  3HCI  requires  94,980  calories. 

The  only  probable  substitutes  for  sodium  in  reducing  alumin- 
ium chloride  are  thus  seen  to  be  magnesium  (whose  cost  will 
probably  be  always  greater  than  that  of  aluminium),  manganese 
(which  may  sometime  be  used  in  the  form  of  ferro-manganese 
for  producing  ferro-aluminium),  and  zinc  (whose  successful 
application  to  this  purpose  would  be  a  most  promising  advance 
in  the  metallurgy  of  aluminium). 

In  1886  Moissan  isolated  fluorine,  and  in  1889  he  and  Berthe- 
lot  measured  the  heat  of  formation  of  hydrofluoric  acid.  With 
this  datum,  it  became  possible  to  calculate  a  table  of  the  heat 
of  formation  of  the  fluorides.*  These  can  now  be  given  as 
follows,  stating  the  heat  evolved  by  combination  with  one 
atomic  weight  (19  kilos)  of  fluorine. 

Element.                                                                    Compound,  Heat  evolved. 

Potassium KF  1 10,000 

Sodium NaF  109,700 

Barium BaF^  112,000 

Strontium SrFj  112,000 

Calcium CaF,  108,000 

Magnesium MgFj  105,000 

Aluminium  AIF3  92,000 

Manganese MnFj  72,000 

Zinc ZnFg  69,000 

Cadmium CdF^  61,000 

Iron FeF^  63,000 

Cobalt C0F2  60,000 

Nickel NiFj  59,500 

Copper CuFj  44,000 

Silver AgF  25,500 

Hydrogen HF  (gas)  37,6oo 

"         "  (in  solution)     49,400 

It  follows  from  an  inspection  of  these  quantities  that  the 
fluorides  are  stronger  compounds  than  either  the  oxides,  chlor- 
ides, bromides  or   iodides.     It  is    also    seen   that  aluminium 

*  See  a  paper  on  this  subject,  by  the  author,  in  the  Journal  of  the  Franklin  Insti- 
tute, June,  1891. 


stands  in  the  same  relative  position  as  in  the  chlorides,  except 
that  it  is  here  stronger  than  manganese  or  zinc.  It  follows  that 
only  sodium,  potassium  or  magnesium  of  the  available  metals 
wilU  reduce  aluminium  fluoride.  For  such  reductions  the  latter 
must  be  liquefied  by  mixture  with  a  fusible  salt  not  acted  on  by 
the  reducing  agent.     Thus,  we*  would  have 

2AIF3  +  6Na=  6NaF+  2AI,  evolving  106,200  calories. 
2A1F3  +  3Mg  =  3MgF2  +  2AI,  evolving  78,000  calories. 
The  reaction  with  zinc  would  absorb  heat  as  follows : 
2AIF3  +  2Zn=  2ZnF2  +  2 Al,  absorbing  138,000  calories. 

While  the  first  two  reactions  take  place  easily,  at  a  red  heat, 
the  latter  is  nearly  impracticable.  The  writer  brought  zinc  into 
contact  with  highly  heated  cryolite  (AlFj.sNaF),  and  obtained 
0.6  per  cent,  of  aluminium  in  the  zinc*  The  temperature  was 
a  bright  red,  and  this  small  amount  of  reduction  shows  that  an 
excess  of  zinc  at  a  high  temperature  will  to  a  small  extent  over- 
come the  affinity  of  aluminium  for  fluorine.  Manganese  in  the 
form  of  ferro-manganese,  might  take  up  even  a  larger  percent- 
age of  aluminium  than  the  above,  yet  no  substantial  amount  of 
reduction  can  be  looked  for  from  these  elements. 

In  order  to  discuss  the  thermal  relations  of  aluminium  sul- 
phide, we  will  make  use  of  the  following  data,  the  heat  devel- 
oped being  per  atomic  weight  (32  kilos)  of  sulphur  combining: 

Element.  Compound.  Calories. 

Alumlnitiin AI283  41,467 

Potassium KjS  103,700 

Sodium Na^S  88,200 

Calcium CaS  92,000 

Strontium SrS  99,200 

Magnesium MgS  79,600 

Manganese MnS  46,400 

Zinc ZnS  41.326 

Iron FeS  23,576 

Copper Cu^S  20,270 

Lead • PbS  20,430 

Hydrogen HjS  4>740 

Carbon CSj  —14,500 

*  See  details  in  Chapter  XII. 


These  figures  point  to  the  easy  reduction  of  aluminium  sul- 
phide by  potassium,  sOdium,  or  magnesium,  and  its  possible 
reduction  by  manganese  and  zinc.  The  other  metals  would 
require  exceptional  conditions,  perhaps,  of  temperature,  for 
their  action.  It  is  interesting  to  note  that  two  observers  have 
determined  from  the  deposition -of  the  metals  from  solution  by 
hydrogen  sulphide,  that  the  order  of  the  afifiinity  of  the  metals 
for  sulphur  is  first  the  alkaline  metals,  then  the  others  in  the 
following  order:  copper,  lead,  zinc,  iron,  manganese,  and  then 
aluminium  and  magnesium — with  the  remark  that  the  affiinities 
of  the  latter  two  for  sulphur  appear  quite  insignificant.  The 
explanation  of  this  difference  is  that  the  metals  last  mentioned 
form  sulphides  which  are  not  stable  in  water,  but  are  immedi- 
ately decomposed  according  to  the  reaction 

3  AI2S3  +  3  H2O  =  AI2O3  +  3H2S,  evolving  77,840  calories, 

while  the  alumina  produced  is  immediately  soluble  in  the  weak 
acid  solution  and  at  once  disappears.  It  follows  that  these  ele- 
ments are  not  precipitated  as  easily  from  solution  as  those 
whose  sulphides  are  not  thus  decomposed  by  water. 

The  reduction  of  aluminium  sulphide  by  copper,  tin  and  iron 
is  in  a  measure  possible  when  the  operation  is  conducted  at  a 
high  temperature  and  there  is  an  excess  of  reducing  metal 
present.  Under  these  conditions,  a  part  of  the  aluminium  sul- 
phide is  reduced  and  an  alloy  formed,  but  such  reactions  can- 
not approach  in  completeness  those  reactions  which  are 
strongly  endothermic.  The  reduction  by  hydrogen  is  seen  to 
be  highly  improbable,  and  by  carbon  still  more  so. 

The  question  of  reducing  aluminium  compounds  by  the  use  of 
electricity  is  a  very  different  question.  Looked  at  as  a  reduc- 
ing or  decomposing  agent,  the  electric  current  is  almighty.  A 
current  with  a  tension  of  i  volt  will  decompose  any  fluoride, 
chloride,  bromide  or  iodide  whose  heat  of  combination  with  one 
atom  weight  of  fluorine  is  less  than  23,000  calories  ;  at  a  tension 
of  two  volts,  any  less  than  46,000  calories ;  and  therefore  at  a 
tension  of  five  volts  would  decompose  the  strongest  of  any  of 


these  salts.  Such  a  current  only  means  half  a  dozen  ordinary 
copper  sulphate  batteries  connected  in  tension.  For  oxides 
and  sulphides,  the  heat  of  combination  with  one-half  an  atomic 
weight  must  be  used,  which  quantity  is  equal  in  combining 
power  to  one  whole  atomic  weight  of  the  above  elements,  and 
then  the  same  rule  applies.  We  can  thus  calculate  the  voltage 
required  to  decompose  the  following  anhydrous  molten  com- 

»                Element.                                                   Fluoride.  Chloride.  Oxide.  Sulphide. 

Potassium 4.8  4.6  2.2  2.3 

Sodium 4.7  4.3  2.2  1 .9 

Barium 4.9  4.3  2.7  2.2 

Strontium 4.9  4.0  2.75  2.2 

Calcium 4.7  3.7  2.85  2.0 

Magnesium 4.6  3.3  3.2  1.7 

Aluminiuin 4.0  2.3  2.8  0.9 

Manganese 3.1  2.4  2.1  l.o 

Zinc 3.0  2.3  1 .9  0.9 

Iron 2.7  1.8  1.5  0.5 

Nickel 2.5  1.6  1.3  0.4 

Copper 1.9  1.4  0.9  0.4 

Silver i.i  1.3  o.l  o.i 

Hydrogen 1.6  i.o  1.5  0.1 

A  critical  comparison  of  these  figures  leads  to  some  very  in- 
teresting conclusions.  We  notice,  in  the  first  place,  that  in  the 
fluorides  there  is  a  very  sharp  drop  after  aluminium  ;  in  these 
salts  aluminium  has  closer  resemblance  to  the  alkaline  earth 
fluorides,  while  manganese  and  zinc  resemble  the  ordinary 
metals.  In  the  chlorides,  there  is  a  sharp  drop  before  alumin- 
ium, leaving  it  in  stronger  resemblance  to  the  zinc,  manganese 
and  lower  metallic  salts.  In  the  oxides,  aluminium  is  again 
classed  with  the  alkaline  earth  metals,  and  sharply  separated 
from  the  lower  metallic  oxides.  Attention  is  particularly  called 
to  the  irregularity  of  the  alkaline  metals,  whose  oxides  are  as 
easily  decomposed  as  those  of  the  metals  below  aluminium. 
This  explains  why  we  can  reduce  these  alkaline  metals  more 
easily  by  carbon  than  we  can  alumina,  and  yet  we  can  use  the 
alkaline  metal  to  react  on  a  salt  of  aluminium  and  get  metallic 


aluminium.  The  high  voltage  required  to  decompose  mag- 
nesium oxide  also  explains  the  wonderful  efficiency  of  mag- 
nesium as  a  reducing  a:gent  when  acting  on  the  oxides.  In  the 
list  of  sulphides,  we  again  notice  a  sharp  drop  before  alumin- 
ium, leaving  it  in  close  correspondance  with  manganese  and 
zinc.  The  very  low  voltage  required  is  also  noticeable ;  a 
single  Daniell  cell  should  be  able  to  produce  decomposition. 
Take  a  bath,  for  instance,  in  which  alumina  is  being  decom- 
posed using  a  tension  of  5  volts,  of  which  2.8  is  absorbed  in 
decomposition  and  2.2  in  overcoming  other  resistances.  If 
aluminium  sulphide  were  the  material  decomposed,  assuming 
other  resistances  the  same  as  before,  the  total  resistance  of  the 
bath  would  be  overcome  by  3.1  volts;  or,  in  other  words,  it 
would  require  only  62  per  cent,  of  the  power  to  produce  the 
same  weight  of  aluminium.  The  sulphide  thus  presents  great 
advantage  in  respect  to  ease  of  decomposition. 

Next  to  the  sulphide,  the  chloride  is  the  easiest  to  decom- 
pose, but  both  these  salts  are  difficult  to  produce,  and  herein 
lies  their  chief  disadvantage. 

It  can  be  furthermore  observed,  that  if  we  mix  these  various 
salts  into  one  bath,  and  use  an  electric  current  carefully  regu- 
lated as  to  tension,  we  can  act  on  pne  ingredient  without  dis- 
turbing to  any  extent  the  others  present.  We  could,  for 
instance,  mix  aluminium  chloride  with  any  fluoride  down  to 
that  of  zinc,  and  by  a  tension  of  2.5  volts  or  a  little  over  sepa- 
rate out  only  alumininum.  We  could  mix  alumina  with  any 
fluoride  or  chloride  above  aluminium  in  the  list,  and  get  only 
aluminium  from  the  bath.  The  fact  is,  however,  that  alumina 
is  not  dissolved  by  the  chlorides,  but  only  by  the  fluorides. 
These  latter  are  therefore  available,  and  are  the  principal  salts 
used  at  present  in  the  aluminium  industry.  Thus,  in  Hall's 
process  we  have  present  in  the  bath 

Alumina  requiring  2.8  volts  for  decomposition. 

Aluminiunl  fluoride         "         4.0         "  " 

Sodium  '■  "         4.7    .     "  ,        •' 

When  the  current  is  passed  through  such  a  mixture,  and  its 


tension  does  not  rise  abnormally  high,' the  bath  being  kept  sat- 
urated with  all  the  aluimina  it  can  dissolve,  the  only  ingredient 
decomposed  is  the  alumina. 

In  Minet's  process  there  are  present : 

Alumina,  requiring  2.8  volts. 

Aluminium  fluoride,         "  4.0     " 

Sodium  fluoride,  "  4^7    " 

Sodium  chloride,  "  4.3     " 

The  minimum  electro-motive  force  required  to  decompose 
this  bath  at  900°  is  2.4  volts;  at  1100°,  2.17  volts.  The  elec- 
tro-motive force  of  carbon  burning  to  carbonic  oxide  at  those 
temperatures  is,  however,  0.65  volts,  so  that  the  voltage  re- 
required  to  decompose  liquid  alumina  at  these  temperatures  is 
0.65  volts  higher  than  the  figure  given.  We  therefore  have 
these  data  for  the  decomposition  of  alumina : 

Voltage  for 



Heat  of  Formation. 



392,600  (solid  aluminium.) 



387,200  (liquid  aluminium). 



424,600  (liquid  aluminium). 



392,600  (liquid  aluminium). 

The  equation  for  the  voltage  required  to  decompose  alumina 
producing  liquid  aluminium  is  therefore : 

V^  2.78  +  0.00129  t — 0.00000128 1'', 

and  the  heat  required  to  decompose  the  molecule  of  alumina  is 

Q  =  387,200+  192  t  —  0.1766 1^ 

This  formula  is  extremely  interesting  from  a  thermo-chemi- 
cal  point  of  view  in  enabling  us  to  calculate  theoretically  the 
temperature  at  which  hydrogen  or  carbon  begins  to  reduce  alu- 
mina. The  heat  of  formation  of  gaseous  water  ,at  zero  is  accu- 
rately known,  and  the  experiments  of  Mallard  and  Le  Chatelier 
on  the  specific  heats  of  hydrogen,  oxygen  and  water  vapor 
enable  us  to  calculate  the  heat  of  formation  at  any  desired  tern- 


perature.  From  these  data  we  calculate  the  heat  of  formation 
of  3HjO  to  be  represented  by  the  formula: 

Q  =  174,300+  7.71  t  — 0.0072  t\ 

Now  to  find  the  temperature  at  which  hydrogen  gas  would  be- 
gin to  reduce  alumina,  we  equate  this  formula  with  the  one 
given  for  the  heat  of  the  formation  of  alumina,  and  have 

387,200  +  192  t  — 0.1766  t''=  174,300+  7.71  t—  0.0072  t'' 

from  which 

t  =  i785°C. 

This  will  be  the  temperature  at  which  the  heat  of  formation 
of  3H2O  will  be  exactly  equal  to  the  heat  of  formation  of  Al^Oj, 
and  consequently  immediately  above  this  temperature  reduc- 
tion will  begin  if  the  physical  conditions  are  favorable  for  the 
reaction  taking  place. 

On  a  similar  principle  we  can  calculate  the  temperature  at 
which  carbon  will  begin  to  reduce  aluminium,  except  that  the 
operation  is  more  difficult  because  of  the  variable  specific  heat 
of  carbon.  I  have  calculated  from  Weber's  results  that  the  heat 
in  carbon  from  zero  to  high  temperatures  may  be  expressed  as 

Q  =  o.5  t  —  120. 

Taking  this  quantity,  in  connection  with  the  specific  heats  of 
oxygen  and  carbonic  oxide  as  determined  by  Mallard  and  Le 
Chatelier  at  high  temperatures,  we  have  for  the  heat  of  forma- 
tion of  3CO  at  any  temperature  t  above  1000°,  the  expression 

Q  =  83.35s  +  8.6472  t  -  0.0009  t^ 

For  finding  the  temperature  at  which  reduction  begins  we  have 

387,200  +  192  t  —  0.1716  t''  =  83,355  +  8.6472  t  — 0.0009  ^^ 

from  which 

t  =  1980°. 


The  temperatures  above  calculated  appear  much  lower  than 
has  heretofore  been  deemed  possible,  but  they  are  supported  by 
experimental  evidence ;  viz.,  the  reduction  of  alumina  by 
hydrogen  performed  by  Warren,  at  a  temperature  which  it  is 
hardly  possible  could  have  been  higher  than  2000° ;  and  the 
production  of  pig-iron  containing  over  i  per  cent,  of  aluminium 
in  a  Pennsylvania  blast  furnace.  The  highest  temperature  at- 
tained in  this  furnace,  not  of  very  modern  construction,  could 
not  have  exceed  2000°  C.      (For  details,  see  Chapter  XII.) 

If  in  place  of  free  hydrogen  gas  or  free  carbon  we  use  as  a 
reducing  agent  a  combination  of  these  two  which  gives  out  heat 
in  its  dissociation  into  carbon  and  hydrogen,  we  would  have  a 
more  efficient  reducing  agent  than  if  the  constituents  were  used 
separately.  Such  a  compound  is  Acetylene,  CjHj,  which  ab- 
sorbs heat  in  its  formation  and  therefore  gives  out  heat  in  its 
decomposition.  At  ordinary  temperatures,  Berthelot  has  found 

C2  +  H2  =  C.2H.2  absorbs  5 1,500  calories. 

We  do  not  know  exactly  how  this  number  varies  with  the  tem- 
perature, as  we  lack  the  specific  heat  of  CJ-Ij,  but  we  know  that 
it  does  not  change  very  much.  We  would  therefore  have  the 
reduction  equation  as  follows — 

AI2O3  +  C.,H2  =  2AI  +  2CO  -I-  H,0 

and  the  heat  requirements  as  follows — 

Reducing AljOa ■•   387,200 -|- 192.61— 0.17161''  (l) 

Developed  in  forming  2CO 55.57°  -f-    S-76t — o.ooo6t''  (2) 

"  "       «         HjO 58,000-1-    2.571— 0.00251^  C3> 

"  "  decomposing  CijHj. 51,500  (4) 

If  we  put  (i)  =  (2)  +  (3)  +  (4)  and  solve  for  t,  we  obtain 
the  theoretical  temperature  at  which  Acetylene  should  begin  to 
reduce  alumina  as 


This  temperature,  it  will  be  observed,  is  not  so  low  as  that 


calculated  for  pure  hydrogen.  Six  months  ago,  this  calculation 
would  have  been  of  purely  scientific  interest,  because  pure 
acetylene  was  a  difiScult  substance  to  procure  ;  but  a  very  prac- 
tical interest  has  been  given  it  by  the  recent  invention  of  Mr. 
Thomas  L.  Willson  of  Brooklyn*,  whereby  pure  acetylene  can 
be  manufactured  at  a  cost  approximating  2  cents  per  pound. 
Since  the  gas  should  theoretically  reduce  double  its  weight  of 
aluminium,  if  perfectly  utilized  for  reduction,  the  cost  of  the  re- 
ducing agent  per  pound  of  aluminium  would  be  very  small.  It 
is  to  be  hoped  that  the  possibility  of  the  above  reaction  may  be 
tested  with  this  powerful  reducing  agent. 

Before  closing  this  subject  of  the  thermal  aspect  of  the  reduc- 
tion of  aluminium  compounds,  it  may  be  interesting  to  notice 
some  of  the  reactions  which  are  of  use  in  the  aluminium  indus- 
try. It  is  well  known  that  while  chlorine  gas  can  be  passed 
over  ignited  alumina  without  forming  aluminium  chloride,  and 
while  carbon  can  be  in  contact  with  alumina  at  a  white  heat 
without  reducing  it,  yet  the  concurrent  action  of  chlorine  and 
carbon  will  change  the  alumina  into  its  chloride,  a  compound 
with  a  lower  heat  of  formation.     Thus — 

AL^Os  -f-  3C  =  AI2  4-  3CO  requires  304,500  cal. 

But  AI2O3  +  3C  +  6C1  =  2AICI2  +  3CO  requires  a  quantity  of 
heat  equal  to  the  304,500  cal.  minus  321,960,  the  heat  of  for- 
mation of  aluminium  chloride,  or  in  other  words,  17,360  cal.  is 
evolved,  showing  that  the  reaction  is  one  of  easy  practicability. 
If  it  be  inquired  whether  there  is  not  some  chloride  which 
would  act  on  alumina  to  convert  it  into  chloride,  we  would  re- 
mark that  if  we  can  find  a  chloride  whose  heat  of  formation  is 
as  much  greater  than  the  heat  of  formation  of  the  correspond- 
ing oxide  as  the  heat  of  formation  of  aluminium  chloride  is 
greater  than  that  of  alumina,  then  such  a  chloride  might  react. 

*  See  description  in  Engineering  and  Mining  Journal,  Dec.  15,  1894. 


To  be  more  particular,  to  convert  alumina  into  aluminium 
chloride,  a  deficit  of  391,600  —  321,960  =  69,640  calories  must 
be  made  up.  If  we  know  of  an  element  which  in  uniting  with 
3  atom  weights  (48  kilos)  of  oxygen  gives  out  69,640  calories 
more  heat,  or  a  still  greater  excess,  than  in  uniting  with  6  atom 
weights  (213  kilos)  of  chlorine,  then  the  chloride  of  that  ele- 
ment might  perform  the  reaction.     Now — 

6Na  +  3O  =  sNajO  evolves  299,280  cal. 
and  6Na  +  6C1  =6NaCl  evolves  586,140  cal. 

leaving  evidently  a  balance  of  286,860  calories  in  the  opposite 
direction  to  what  we  are  looking  for.  And  so  for  every  metal 
except  aluminium,  I  find  the  heat  of  formation  of  its  chloride 
greater  than  an  equivalent  quantity  of  its  oxide.  The  only 
element  which  I  know  to  possess  the  opposite  property  is 
hydrogen,  for — 

6H  +  3O  —  3H2O  evolves  205,080  cal. 
and  6H  +  6C1  =  6HC1  evolves  132,000  cal. 

and  therefore  the  reaction — 

AI2O3  +  6HC1  =  2AICI3  +  3H2C 

would  evolve  according  to  our  calculations  (205, 080 — 132,000) — 
69,640=3,440  calories,  and  would  be  thermally  considered  a  pos- 
sible reaction.  Moreover,  as  a  secondary  effect,  the  water  formed 
is  immediately  seized  by  the  aluminium  chloride,  for  the  reaction 

2AICI3  +  3H2O  =  2AICI3.3H2O  evolves  153,690  cal. 

and  thus  increases  the  total  heat  developed  in  the  decom- 
position of  the  alumina  to  158,  [30  calories.  The  result  of 
this  reaction  is  therefore  the  hydrated  chloride,  which  is  of  no 
value  for  reduction  by  sodium,  since  when  heated  it  decom- 
poses into  alumina  and  hydrochloric  acid  again,  that  is,  it  will 
decompose  before  giving  up  its  water,  and  the  water  if  unde- 
composed,  or  the  acid  if  it  decomposes,  simply  unites  with  the 


sodium  without  affecting  the  alumina.  The  immense  heat  of 
hydration,  153,690  calories,  is  so  much  greater  than  any  other 
known  substance,  that  it  is  vain  that  we  seek  for  any  material 
which  might  abstract  the  water  and  leave  anhydrous  aluminium 

Analagous  to  the  reaction  by  which  aluminium  chloride  is 
formed  from  alumina  is  the  reaction  made  use  of  for  obtaining 
aluminium  sulphide,  yet  with  some  thermal  considerations  of  a 
different  and  highly  interesting  kind.  If  a  mixture  of  alumina 
and  carbon  is  ignited  and,  instead  of  chlorine,  sulphur  vapor  is 
passed  over  it,  no  aluminium  sulphide  will  be  formed.  An  ex- 
planation of  this  fact  is  seen  on  discussing  the  proposed  reac- 
tion thermally. 

AI2O3  +  3C  -I-  3S  =  AI2S3  +  3CO  requires  180,200  cal. 

It  will  be  remembered  that  the  similar  reaction  with  chlorine 
evolved  17,360  calories;  the  quantity  causing  this  difference  is 
the  heat  of  combination  of  aluminium  sulphide,  which  is  321,960 
— 124,400  =  197,560  calories  less  than  that  of  aluminium 
chloride,  changing  the  excess  of  17,360  calories  into  a  deficit  of 
180,200  calories.  This  large  negative  quantity  shows  a  priori 
that  the  reaction  could  be  made  to  occur  only  under  excep- 
tional conditions,  and  its  non-occurrence  under  all  conditions 
so  far  tried  gives  evidence  of  the  utility  of  the  study  of  thermo- 
chemistry, at  least  as  a  guide  to  experiment.  However,  while 
carbon  and  sulphur  cannot  convert  alumina  into  aluminium  sul- 
phide, carbon  bisulphide  can,  for  a  current  of  the  latter  led  over 
ignited  alumina  converts  it  into  aluminium  sulphide.  The  re- 
action taking  place  is 

Al^Oa  +  3CS2  =  A1,S3  +  3COS. 

Now,  since  carbon  and  sulphur  by  themselves  could  not  per- 
form the  reaction,  we  should  be  very  apt  to  reason  that  a  com- 
pound of  carbon  and  sulphur  would  be  still  less  able  to  do  so, 
since    the  heat   absorbed    in  dissociating  the   carbon-sulphur 


compound  would  cause  a  still  greater  deficit  of  heat.  But  here 
-is  precisely  the  explanation  of  the  paradox.  Carbon  bisulphide 
is  one  of  those  compounds,  not  frequent,  which  has  a  negative 
heat  of  formation  ( — 29,000  calories),  i.  e.,  heat  is  absorbed  in 
large  quantity  in  its  formation,  and  therefore,  per  contra,  heat 
is  given  out  in  the  same  quantity  in  its  decomposition.  The 
heat  of  formation  of  carbon  oxysulphide  being  37,030  calories, 
we  can  easily  compute  the  thermal  value  of  the  reaction  just 

Ifeat  absorbed. 

Decomposition  of  alumina 391,600  cal. 

Heat  developed. 

Decomposition  of  carbon  bisulphide 87,000 

Formation  of  carbon  oxysulphide 1 1 1,090 

"  of  aluminium  sulphide   124,400 

322,490  cal. 

Deficit  of  heat 69,1 10   " 

It  is  thus  seen  that  the  reaction  with  carbon  bisulphide  is 
less  than  one-half  as  strongly  negative  as  the  reaction  with  car- 
bon and  sulphur  alone,  and  we  therefore  have  an  explanation 
of  the  fact  that  the  reaction  with  carbon  bisulphide  is  easily 
practicable,  while  the  other  is  not.  We  do  not  know  enough 
about  the  variation  of  the  heats  of  formation  of  aluminium  sul- 
phide and  carbon  oxysulphide  to  be  able  to  make  calculations 
as  accurately  as  was  possible  with  the  question  of  reducing  alu- 
mina, but  if  all  the  heats  of  formation  remained  constant  except 
that  of  alumina,  the  69,000  calories  deficit  would  be  made  up 
by  the  decrease  in  the  heat  of  formation  of  chat  substance  at 
975O  C,  which  is  somewhere  about  the  temperature  at  which 
the  reaction  really  takes  place. 



The  methods  comprised  under  this  heading  may  be  con- 
veniently divided  into  two  classes  : — 

I.  Methods  based  on  the  reduction  of  aluminium  chloride 

or  aluminium-sodium  chloride. 
II.  Methods  based  on  the  reduction  of  cryolite  or  aluminium 


The  methods  here  included  can  be  most  logically  presented 
by  taking  them  in  chronological  order. 

Oerstedt's  Experiments  (1824). 

After  Davy's  unsuccessful  attempts  to  isolate  aluminium  by 
the  battery,  in  1807,  the  next  chemist  to  publish  an  account  of 
attempts  in  this  direction  was  Oerstedt,  who  published  a  paper 
in  1824  in  a  Swedish  periodical.*  Oerstedt's  original  paper  is 
thus  translated  into  Berzelius's  "  Jahresbericht  :"f 

"  Oerstedt  mixes  calcined  and  pure  alumina,  quite  freshly 
prepared,  with  powdered  charcoal,  puts  it  in  a  porcelain  retort, 
ignites  and  leads  chlorine  gas  through.  The  coal  then  reduces 
the  alumina,  and  there  results  aluminium  chloride  and  carbonic 
oxide,  and  perhaps  also  some  phosgene,  COCI2 ;  the  alumin- 
ium chloride  is  caught  in  the  condenser  and  the  gases  escape. 
The  sublimate  is  white,  crystalline,  melts  about  the  tempera- 
ture of  boiling  water,  easily  attracts  moisture,  and  evolves  heat 

*  Oversigt  over  det  K.     Danske  Videnskabemes  Selkabs  Forhandlingar  og   dets 
Medlemmers  Arbeider.     May,  1824,  to  May,  1825,  p.  15. 
fBerz.  Jahresb.  der  Chemie,  1827,  vi.  1 1 8. 



when  in  contact  with  water.  If  it  is  mixed  with  a  concentrated 
potassium  amalgam  and  heated  quickly,  it  is  transformed  ;  there 
results  potassium  chloride,  and  the  aluminium  unites  with  the 
mercury.  The  new  amalgam  oxidizes  in  the  air  very  quickly, 
and  gives  as  residue  when  distilled  in  a  vacuum  a  lump  of  metal 
resembling  tin  in  color  and  lustre.  In  addition,  Oerstedt  found 
many  remarkable  properties  of  the  metal  and  of  the  amalgam, 
but  he  holds  them  for  a  future  communication  after  further  in- 

Oerstedt  did  not  publish  any  other  paper,  and  the  next  ad- 
vance in  the  science  is  credited  to  Wohler,  whom  all  agree  in 
naming  as  the  true  discoverer  of  the  metal. 

Wohler' s  Experiments  (1827). 

In  the  following  article  from  Poggendorff 's  Annalen,*  Wohler 
reviews  the  article  of  Oerstedt's  given  above,  and  continues  as 
follows : — 

"  I  have  repeated  this  experiment  of  Oerstedt,  but  achieved 
no  very  satisfactory  result.  By  heating  potassium  amalgam 
with  aluminium  chloride  and  distilling  the  product,  there  re- 
mained behind  a  gray,  melted  mass  of  metal,  but  which,  by 
raising  the  heat  to  redness,  went  ofif  as  green  vapor  and  distilled 
as  pure  potassium.  I  have  therefore  looked  around  for  another 
method  or  way  of  conducting  the  operation,  but,  unpleasant  as 
it  is  to  say  it,  the  reduction  of  the  aluminium  fails  each  time. 
Since,  however,  Herr  Oerstedt  remarks  at  the  end  of  his  paper 
that  he  did  not  regard  his  investigations  in  aluminium  as  yet 
ended,  and  already  several  years  have  passed  since  then,  it 
looks  as  if  I  had  taken  up  one  of  those  researches  begun  aus- 
piciously by  another  (but  not  finished  by  him),  because  it 
promised  new  and  splendid  results.  I  must  remark,  however, 
that  Herr  Oerstedt  has  indirectly  by  his  silence  encouraged  me 
to  try  to  attain  to  further  results  myself.  Before  I  give  the  art 
how  one  can  quite  easily  reduce  the  metal,  I  will  say  a  few 
words  about  aluminium  chloride  and  its  production  (see  p.  152). 

*  Pogg.  Ann.,  1827,  ii.  147. 


"  I  based  the  method  of  reducing  aluminium  on  the  reaction 
of  aluminium  chloride  on  potassium,  and  on  the  property  of  the 
metal  not  to  oxidize  in  water.  I  warmed  in  a  glass  retort  a 
small  piece  of  the  aluminium  salt  with  some  potassium,  and  the 
retort  was  shattered  with  a  strong  explosion.  I  tried  then  to  do 
it  in  a  small  platinum  crucible,  in  which  it  succeeded  very  well. 
The  reaction  is  always  so  violent  that  the  cover  must  be  weighted 
down,  or  it  will  be  blown  off;  and  at  the  moment  of  reduction, 
although  the  crucible  be  only  feebly  heated  from  outside,  it 
suddenly  glows  inside,  and  the  platinum  is  almost  torn  by  the 
sudden  shocks.  In  order  to  avoid  any  mixture  of  platinum 
with  the  reduced  aluminium,  I  next  made  the  reduction  in  a 
porcelain  crucible,  and  succeeded  then  in  the  following  manner : 
Put  in  the  bottom  of  the  crucible  a  piece  of  potassium  free  from 
carbon  and  oil,  and  cover  this  with  an  equal  volume  of  pieces 
of  aluminium  chloride.  Cover  and  heat  over  a  spirit  lamp,  at 
first  gently,  that  the  crucible  be  not  broken  by  the  production  of 
heat  inside,  and  then  heat  stronger,  at  last  to  redness.  Cool, 
and  when  fully  cold  put  it  into  a  glass  of  cold  water.  A  gray 
powder  separates  out,  which  on  nearer  observation,  especially 
in  sunlight,  is  seen  to  consist  of  little  flakes  of  metal.  After  it 
has  separated,  pour  off  the  solution,  filter,  wash  with  cold 
water,  and  dry;   this  is  the  aluminium." 

In  reality,  this  powder  possessed  no  metallic  properties,  and 
moreover,  it  contained  potassium  and  aluminium  chloride, 
which  gave  it  the  property  of  decomposing  water  at  100°.  To 
avoid  the  loss  of  aluminium  chloride  by  volatilization  at  the 
high  heat  developed  during  the  reaction,  Liebig  afterwards 
made  its  vapors  pass  slowly  over  some  potassium  placed  in  a 
long  glass  tube.  This  device  of  Liebig  is  nearly  the  arrange- 
ment which  Wohler  adopted  later,  in  1845,  ^nd  which  gave  him 
much  better  results. 

Wbklcr's  Experiments  ( 1 845 ) . 
The  following  is  Wohler's  second  paper  published  in  1845  ■* 

*  Liebig's  Annalen,  53,  422. 


"  On  account  of  the  violent  incandescence  with  which  the 
reduction  of  aluminium  chloride  by  potassium  is  accompanied, 
this  operation  requires  great  precautions,  and  can  be  carried 
out  only  on  a  small  scale.  I  took  for  the  operation  a  platinum 
tube,  in  which  I  placed  aluminium  chloride,  and  near  it  some 
potassium  in  a  platinum  boat.  I  heated  the  tube  gently  at  first, 
then  to  redness.  But  the  reduction  may  also  be  done  by  put- 
ting potassium  in  a  small  crucible,  which  is  placed  inside  a 
larger  one,  and  the  space  between  the  two  filled  with  aluminium 
chloride.  A  close  cover  is  put  over  the  whole,  and  it  is  heated. 
Equal  volumes  ot  potassium  and  the  aluminium  salt  are  the 
best  proportions  to  employ.  After  cooling,  the  tube  or  cruci- 
ble is  put  in  a  vessel  of  water.  The  metal  is  obtained  as  a  gray 
metallic  powder,  but  on  closer  observation  one  can  see  even 
with  the  naked  eye  small  tin-white  globules,  some  as  large  as 
pins'  heads.  Under  the  microscope  magnifying  two  hundred 
diameters,  the  whole  powder  resolves  itself  into  small  globules, 
several  of  which  may  sometimes  be  seen  sticking  together, 
showing  that  the  metal  was  melted  at  the  moment  of  reduction. 
A  beaten-out  globule  may  be  again  melted  to  a  sphere  in  a 
bead  of  borax  or  salt  of  phosphorus,  but  rapidly  oxidizes  dur- 
ing the  operation,  and  if  the  heat  is  continued,  disappears 
entirely,  seeming  either  to  reduce  boric  acid  in  the  borax  bead, 
or  phosphoric  acid  in  the  salt  of  phosphorus  bead.  I  did  not 
succeed  in  melting  together  the  pulverulent  aluminium  in  a 
crucibe  with  borax,  at  a  temperature  which  would  have  melted 
cast-iron,  for  the  metal  disappeared  entirely  and  the  borax  be- 
came a  black  slag.  It  seems  probable  that  aluminium,  being 
lighter  than  molten  borax,  swims  on  it  and  burns.  The  white 
metallic  globules  had  the  color  and  lustre  of  tin.  It  is  perfectly 
malleable  and  can  be  hammered  out  to  the  thinnest  leaves. 
Its  specific  gravity,  determined  with  two  globules  weighing  32 
milligrammes,  was  2.50,  and  with  three  hammered- out  globules 
weighing  34  milligrammes,  2.67.  On  account  of  their  lightness 
these  figures  can  only  be  approximate.  It  is  not  magnetic, 
remains  white  in  the  air,  decomposes  water  at    100°,  not  at 


usual  temperatures,  and  dissolves  completely  in  caustic  potash 
(KOH).  When  heated  in  oxygen  almost  to  melting,  it  is  only 
superficially  oxidized,  but  it  burns  like  zinc  in  a  blast-lamp 

These  results  of  Wohler's,  especially  the  determination  of 
specific  gravity,  were  singularly  accurate  when  we  consider 
that  he  established  them  working  with  microscopic  bits  of 
the  metal,  It  was  just  such  work  that  established  Wohler's 
fame  as  an  investigator.  However,  we  notice  that  his  metal 
differed  from  aluminium  as  we  know  it  in  several  important 
respects,  in  speaking  of  which  Deville  says:  "All  this  time 
the  metal  obtained  by  Wohler  was  far  from  being  pure ;  it  was 
very  difficultly  fusible,  owing,  without  doubt,  to  the  fact  that 
it  contained  platinum  taken  from  the  vessel  in  which  it  had 
been  prepared.  It. is  well  known  that  these  two  metals  com- 
bine very  easily  at  a  gentle  heat.  Moreover,  it  decomposed 
water  at  100°,  which  must  be  attributed  either  to  the  presence 
of  potassium  or  to  aluminium  chloride,  with  which  the  metal 
might  have  been  impregnated :  for  aluminium  in  presence  of 
aluminium  chloride  in  effect  decomposes  water  with  evolution 
of  hydrogen." 

After  Wohler's  paper  in  1845,  the  next  improvement  is  that 
introduced  by  Deville  in  1854-55,  and  this  is  really  the  date  at 
which  aluminium,  the  metal,  became  known  and  its  true  proper- 
ties established. 

Deville  s  Experiments  (1854). 

The  results  of  this  chemist's  investigations  and  success  in 
obtaining  pure  aluminium  were  first  made  public  at  the  seance 
of  the  French  Academy,  August  14,  1854,  and  included  men- 
tion of  an  electrolytic  method  of  reduction  (see  Chap.  XI.),  as 
well  as  of  the  following  on  reduction  by  sodium.* 

"  The  following  is  the  best  method  for  obtaining  aluminium 
chemically  pure  in  the  laboratory.  Take  a  large  glass  tube 
about  four  centimeters  in  diameter,  and  put  into  it  200  or  300 

*  Ann.  de  Phys.  et  de  Chim.,  xliii.  24. 


grammes  of  pure  aluminium  chloride  free  from  iron,  and  isolate 
it  between  two  stoppers  of  amianthus  (fine,  silky  asbestos). 
Hydrogen,  well  dried  and  free  from  air,  is  brought  in  at  one 
end  of  the  tube.  The  aluminium  chloride  is  heated  in  this  cur- 
rent of  gas  by  some  lumps  of  charcoal  in  order  to  drive  ofif 
hydrochloric  acid  or  sulphides  of  chlorine  or  of  silicon,  with 
which  it  is  always  impregnated.  Then  there  are  introduced  into 
the  tube  porcelain  boats,  as  large  as  possible,  each  containing 
several  grammes  of  sodium,  which  was  previously  rubbed  quite 
dry  between  leaves  of  filter  paper.  The  tube  being  full  of 
hydrogen,  the  sodium  is  melted,  the  aluminium  chloride  is 
heated  and  distils,  and  decomposes  in  contact  with  the  sodium 
with  incandesence,  the  intensity  of  which  can  be  moderated  at 
pleasure.  The  operation  is  ended  when  all  the  sodium  has  dis- 
appeared, and  when  the  sodium  chloride  formed  has  absorbed 
so  much  aluminium  chloride  as  to  be  saturated  with  it.  The 
aluminium  which  has  been  formed  is  held  in  the  double  chloride 
of  sodium  and  aluminium,  AlClg.NaCl,  a  compound  very  fusible 
and  very  volatile.  The  boats  are  then  taken  from  the  glass 
tube,  and  their  entire  contents  put  in  boats  made  of  retort  car- 
bon, which  have  been  previously  heated  in  dry  chlorine  in  order 
to  remove  all  siliceous  and  ferruginous  matter.  These  are  then 
introduced  into  a  large  porcelain  tube,  furnished  with  a  pro- 
longation and  traversed  by  a  current  of  hydrogen,  dry  and  free 
from  air.  This  tube  being  then  heated  to  bright  redness,  the 
aluminium-sodium  chloride  distils  without  decomposition  and 
condenses  in  the  prolongation.  There  is  found  in  the  boats, 
after  the  operation,  all  the  aluminium  which  had  been  reduced, 
collected  in  at  most  one  or  two  small  buttons.  The  boats  when 
taken  from  the  tube  should  be  nearly  free  from  aluminium- 
sodium  chloride,  and  also  from  sodium  chloride.  The  buttons 
of  aluminium  are  united  in  a  small  earthenware  crucible,  which 
is  heated  as  gently  as  possible,  just  sufificient  to  melt  the  metal. 
The  latter  is  pressed  together  and  skimmed  clean  by  a  small 
rod  or  tube  of  clay.  The  metal  thus  collected  may  be  very 
suitably  cast  in  an  ingot  mould." 


The  later  precautions  added  to  the  above  given  process  were 
principally  directed  towards  avoiding  the  attacking  of  the  cruci- 
ble, which  always  takes  place  when  the  metal  is  melted  with  a 
flux,  and  the  aluminium  thereby  made  more  or  less  siliceous. 
The  year  following  the  publication  of  these  results,  this  labora- 
tory method  was  carried  out  on  a  large  scale  at  the  chemical 
works  at  Javel. 

Deville's  Methods  (1855). 

The  methods  about  to  be  given  are  those  which  were  devised 
in  Deville's  laboratory  at  the  Ecole  Normale,  during  the  winter 
of  1854-55,  and  applied  on  a  large  scale  at  Javel,  during  the 
spring  of  1855  (March-July).  The  Emperor  Napoleon  III. 
defrayed  the  expenses  of  this  installation.  Descriptions  of  the 
methods  used  for  producing  alumina,  aluminium  chloride  and 
sodium  at  Javel  can  be  found  under  their  respective  headings 
(pp.  134,  153,  180),  We  here  confine  our  description  to 
the  mode  of  reducing  the  aluminium  chloride  by  sodium,  and 
the  remarks  incident  thereto.  The  process  has  at  present 
only  an  historic  interest,  as  it  was  soon  modified  in  its  details 
so  as  to  be  almost  entirely  changed.  The  following  is  Deville's 
description :  — 

"  Perfectly  pure  aluminium. — To  obtain  aluminium  perfectly 
pure  it  is  necessary  to  employ  materials  of  absolute  purity,  to 
reduce  the  metal  in  presence  of  a  completely  volatile  flux,  and 
finally  never  to  heat,  especially  with  a  flux,  in  a  siliceous  vessel 
to  a  high  temperature. 

"  Pure  materials. — The  necessity  of  using  absolutely  pure 
materials  is  easy  to  understand ;  all  the  metallic  impurities  are 
concentrated  in  the  aluminium,  and  unfortunately  I  know  no 
absolute  method  of  purifying  the  metal.  Thus,  suppose  we 
take  an  alum  containing  o.i  per  cent,  of  iron  and  11  per  cent, 
of  alumina;  the  alumina  derived  from  it  will  contain  i  per 
cent,  of  iron,  and  supposing  the  alumina  to  give  up  all  the  alu- 
minium in  it,  the  metal  will  be  contaminated  with  2  per  cent, 
of  iron. 



'^Influence  of  flux  or  slag. — The  flux,  or  the  product  of  the 
reaction  of  the  sodium  on  the  aluminous  material,  ought  to  be 
volatile,  that  one  may  separate  the  aluminium  by  heat  from  the 
material  with  which  it  has  been  in  contact,  and  with  which  it 
remains  obstinately  impregnated  because  of  its  small  specific 

"  Influence  of  the  vessel. — The  siliceous  vessels  in  which 
aluminium  is  received  or  melted  give  it  necessarily  a  large 
quantity  of  silicon,  a  very  injurious  impurity.  Silicon  cannot 
be  separated  from  aluminium  by  any  means,  and  the  siliceous 
aluminium  seems  to  have  a  greater  tendency  to  take  up  more 
silicon  than  pure  aluminium,  so  that  after  a  small  number  of 
remeltings  in  siliceous  vessels  the  metal  becomes  so  impure  as 
to  be  almost  infusible. 

In  order  to  avoid  the  dangers  pointed  out  above,  Deville  re- 
commended following  scrupulously  the  following  details  in 
order  to  get  pure  aluminium. 

"  Reduction  of  solid  sodium. — The  crude  aluminium  chloride 
placed  in  the  cyHnder  A  (Fig.  23),  is  vaporized  by  the  fire  and 


Fig.  24. 



I  to.»»iaa  Y^s;^  teMaa  "T 

passes  through  the  tube  to  the  cylinder  B,  containing  60  to  80 
kilos  of  iron  nails  heated  to  a  dull-red  heat.  The  iron  retains 
as  relatively  fixed  ferrous  chloride,  the  ferric  chloride  and 
hydrochloric  acid  which  contaminate  the  aluminium  chloride, 
and  likewise  transforms  any  sulphur  dichloride  (SCl^)  in  it  into 
ferrous  chloride  and  sulphide  of  iron.  The  vapors  on  passing 
out  of  B  through  the  tube,  which  is  kept  at  about  300°,  deposit 


spangles  of  ferrous  chloride,  which  is  without  sensible  tension 
at  that  temperature.  The  vapors  then  enter  D,  a  cast-iron 
cylinder  in  which  are  three  cast-iron  boats  each  containing  500 
grms.  of  sodium.  It  is  sufficient  to  heat  this  cylinder  barely  to 
a  dull-red  heat  in  its  lower  part,  for  the  reaction  once  com- 
menced disengages  enough  heat  to  complete  itself,  and  it  is 
often  necessary  to  take  awav  all  the  fire  from  it.  There  is  at 
first  produced  in  the  first  boat  some  aluminium  and  some  sod- 
ium chloride,  which  latter  combines  with  the  excess  of  alumin- 
ium chloride  to  form  the  volatile  aluminium-sodium  chloride, 
AlClj.NaCl.  These  vapors  of  double  chloride  condense  on  the 
second  boat  and  are  decomposed  by  the  sodium  into  alumin- 
ium and  sodium  chloride.  A  similar  reaction  takes  place  in 
the  third  boat  when  all  the  sodium  of  the  second  has  disap- 
peared. When  on  raising  the  cover  it  is  seen  that  the 
sodium  of  the  last  boat  is  entirely  transformed  into  a  lumpy 
black  material,  and  that  the  reactions  are  over,  the  boats 
are  taken  out,  immediately  replaced  by  others,  and  are  al- 
lowed to  cool  covered  by  empty  boats.  In  this  first  opera- 
tion the  reaction  is  rarely  complete,  for  the  sodium  is 
protected  by  the  layer  of  sodium  chloride  formed  at  its  ex- 
pense. To  make  this  disappear,  the  contents  of  the  boats  are 
put  into  cast-iron  pots  or  earthen  crucibles,  which  are  heated 
until  the  aluminium  chloride  begins  to  volatilize,  when  the  so- 
dium will  be  entirely  absorbed  and  the  aluminium  finally  re- 
mains in  contact  with  a  large  excess  of  its  chloride,  which  is 
indispensable  for  the  success  of  the  operation.  Then  the  pots 
or  crucibles  are  cooled,  and  there  is  taken  from  the  upper  part 
of  their  contents  a  layer  of  sodium  chloride  almost  pure,  while 
underneath  are  found  globules  of  aluminium  which  are  sepa- 
rated from  the  residue  by  washing  with  water.  Unfortunately 
the  water  in  dissolving  the  aluminium  chloride  of  the  flux  exer- 
cises on  the  metal  a  very  rapid  destructive  action,  and  only 
the  globules  larger  than  the  head  of  a  pin  are  saved  from  this 
washing.  These  are  gathered  together,  dried,  melted  in  an 
earthen    crucible,    and    pressed    together    with     a    clay    rod. 


The  button  is  then  cast  in  an  ingot  mould.  It  is  important  in 
this  operation  to  employ  only  well-purified  sodium,  and  not  to 
melt  the  aluminium  if  it  still  contains  any  sodium,  for  in  this 
case  the  metal  takes  fire  and  burns  as  long  as  any  of  the  alka- 
line metal  remains  in  it.  In  such  a  case  it  is  necessary  to  re- 
melt  in  presence  of  a  little  aluminium-sodium  chloride. 

"  Such  is  the  detestable  process  by  means  of  which  were  made 
the  ingots  of  aluminium  sent  to  the  Exhibition  (1855).  To 
complete  my  dissatisfaction  at  the  processs,  pressed  by  time  and 
ignorant  of  the  action  of  copper  on  aluminium,  I  employed  in 
almost  all  my  experiments  reaction  cylinders  and  boats  of  cop- 
per, so  that  the  aluminium  I  took  from  them  contained  such 
quantities  of  this  metal  as  to  form  a  veritable  alloy.  Moreover,  it 
had  lost  almost  all  ductility  and  malleability,  had  a  disagreeable 
gray  tint,  and  finally  at  the  end  of  two  months  it  tarnished  by 
becoming  covered  with  a  black  layer  of  oxide  or  sulphide  of 
copper,  which  could  only  be  removed  by  dipping  in  nitric  acid. 
But,  singular  to  relate,  an  ingot  of  virgin  silver  which  had  been 
put  alongside  the  aluminium  that  the  public  might  note  easily 
the  difference  in  color  and  weight  of  the  two  metals,  was 
blackened  still  worse  than  the  impure  aluminium.  Only  one  of 
the  bars  exhibited,  which  contained  no  copper,  remained  un- 
altered from  the  day  of  its  manufacture  till  now  (1859).  It 
was  some  of  this  cupreous  aluminium  that  I  sent  to  M. 
Regnault,  who  had  asked  me  for  some  in  order  to  determine  its 
specific  heat.  I  had  cautioned  him  at  the  time  of  the  number 
and  nature  of  the  impurities  which  it  might  contain,  and  the 
analysis  of  M.  Salvetat,  which  is  cited  in  the  memoir  of 
Regnault,  accords  with  the  mean  composition  of  the  specimens 
that  I  had  produced  and  analyzed  at  that  time  (see  p.  54, 
Analysis  i).  It  is  to  be  regretted  that  I  gave  such  impure 
material  to  serve  for  determinations  of  such  splendid  precision. 
I  was  persuaded  to  do  so  only  by  the  entreaties  of  M. 
Regnault,  who  could  not  wait  until  I  prepared  him  better.  It  is 
also  this  cupreous  aluminium  which  M.  Hulot  has  called  '  hard 
aluminium,'  in  a  note  on  the  physical  properties  of  this  metal 


which  he  addressed  to  the  Academy.  Hulot  has  remarked 
that  this  impure  metal,  which  is  crystalline  in  structure,  after 
having  been  compressed  between  the  dies  of  the  coining  press 
may  lose  its  crystalline  structure,  to  which  it  owes  its  brittle- 
ness,  and  become  very  malleable.  It  possesses  then  such 
strength  that  it  works  well  in  the  rolls  of  a  steel  rolling  mill. 
Further,  this  'hard  aluminium'  becomes  quite  unalterable  when 
it  has  thus  lost  its  texture. 

"Reduction  by  sodium  vapor. — This  process,  which  I  have  not 
perfected,  is  very  easy  to  operate,  and  gave  me  very  pure  metal 
at  the  first  attempt.  I  operate  as  follows :  I  fill  a  mercury  bot- 
tle with  a  mixture  of  chalk,  carbon,  and  carbonate  of  soda,  in 
the  proportions  best  for  generating  sodium.  An  iron  tube 
about  ten  centimetres  long  is  screwed  to  the  bottle,  and  the 
whole  placed  in  a  wind  furnace,  so  that  the  bottle  is  heated  to 
red-white  and  the  tube  is  red  to  its  end.  The  end  of  the  tube 
is  then  introduced  into  a  hole  made  in  a  large  earthen  crucible 
about  one-fourth  way  from  the  bottom,  so  that  the  end  of  the 
tube  just  reaches  the  inside  surface  of  the  crucible.  The  car- 
bonic oxide  (CO)  disengaged  burns  in  the  bottom  of  the  cru- 
cible, heating  and  drying  it ;  afterwards  the  sodium  flame 
appears,  and  then  pieces  of  aluminium  chloride  are  thrown  into 
the  crucible  from  time  to  time.  The  salt  volatilizes  and  de- 
composes before  this  sort  of  tuyere,  from  which  issues  the 
reducing  vapor.  More  aluminium  salt  is  added  when  the 
vapors  coming  from  the  crucible  cease  to  be  acid,  and  when 
the  flame  of  sodium  burning  in  the  atmosphere  of  aluminium 
chloride  loses  its  brightness.  When  the  operation  is  finished, 
the  crucible  is  broken  and  there  is  taken  from  the  walls  below 
the  entrance  of  the  tube  a  saline  mass  composed  of  sodium 
chloride,  a  considerable  quantity  of  globules  of  aluminium,  and 
some  sodium  carbonate,  which  latter  is  in  larger  quantity  the 
slower  the  operation  was  performed.  The  globules  are  de- 
tached by  plunging  the  saline  mass  into  water,  when  it  be- 
comes necessary  to  notice  the  reaction  of  the  water  on  litmus. 
If  the  water  becomes  acid,  it  is  renewed  often ;   if  alkaline,  the 


mass,  impregnated  with  metal,  must  be  digested  in  nitric  acid, 
diluted  with  three  or  four  volumes  of  water,  and  so  the  metal  is 
left  intact.  The  globules  are  reunited  by  melting  with  the 
precautions  before  given." 

Deville's  Process  (1859). 

The  process  then  in  use  at  Nanterre  was  based  on  the  use  of 
aluminium-sodium  chloride,  which  was  reduced  by  sodium, 
with  cryolite  or  fluorspar  as  a  flux.  The  methods  of  preparing 
each  of  these  materials  were  carefully  studied  out  at  the  chem- 
ical works  of  La  Glaciere,  where,  from  April,  1856,  to  April, 
1857,  the  manufacture  of  aluminium  was  carried  on  by  a  com- 
pany formed  by  Deville  and  a  few  friends,  and  from  thence 
proceeded  the  actual  system  which  was  established  at  Nanterre 
under  the  direction  of  M.  Paul  Morin  when  the  works  at  La 
Glaciere  were  closed.  The  methods  of  preparation  of  alumina, 
aluminium-sodium  chloride  and  sodium  used  at  Nanterre  are 
placed  under  their  respective,  headings  (pp.  137,  154,  190). 

In  the  first  year  that  the  works  at  Nanterre  were  in  opera- 
tion there  were  made : 

Aluminium-sodium  chloride 10,000  kilos. 

Sodium 2,000     " 

Aluminium 600      " 

The  metal  prepared  improved  constantly  in  quality,  M.  Morin 
profiting  continually  by  his  experience  and  improving  the 
practical  details  constantly,  so  that  the  aluminium  averaged,  in 
1859,  gj  per  cent.  pure.     (See  Analysis  9,  p.  54.) 

As  to  the  rationale  of  the  process  used,  aluminium  chloride 
was  replaced  by  aluminium-sodium  chloride  because  the  latter 
is  less  deliquescent  and  less  difficult  of  preservation ;  but  the. 
small  amount  of  moisture  absorbed  by  the  double  chloride  is 
held  very  energetically,  at  a  high  temperature  giving  rise  to 
some  alumina,  which  encloses  the  globules  of  metal  with  a  thin 
coating,  and  so  hinders  their  easy  reunion  to  a  button.  Deville 
remarked  that  the  presence  of  fluorides  facilitated  the  reunion 


of  these  globules,  which  fact  he  attributed  to  their  dissolving 
the  thin  coat  of  alumina ;  so  that  the  employment  of  a  fluoride 
as  a  flux  became  necessary  to  overcome  the  effect  produced 
primarily  by  the  aluminium-sodium  chloride  holding  moisture 
so  energetically.  Deville  gives  the  following  account  of  the 
development  of  these  improvements  :  "The  facility  with  which 
aluminium  unites  in  fluorides  is  due  without  doubt  to  the  prop- 
erty which  these  possess  of  dissolving  the  alumina  on  the  sur- 
face of  the  globules  at  the  moment  of  their  formation,  and 
which  the  sodium  is  unable  to  reduce.  I  had  experienced  great 
difificulty  by  obtaining  small  quantities  of  metal  poorly  united, 
when  I  reduced  the  aluminium-sodium  chloride  by  sodium ; 
M.  Rammelsberg,  who  often  made  the  same  attempts,  tells  me 
he  has  had  a  Hke  experience.  But  I  am  assured  by  a  scrupu- 
lous analysis  that  the  quantity  of  metal  reduced  by  the  sodium 
is  exactly  that  which  theory  indicates,  although  after  many 
operations  there  is  found  only  a  gray  powder,  resolving  itself 
under  the  microscope  into  a  multitude  of  small  globules.  The 
fact  is  simply  that  aluminium-sodium  chloride  is  a  very  poor 
flux  for  aluminium.  MM.  Morin,  Debray,  and  myself  have 
undertaken  to  correct  this  bad  effect  by  the  introduction  of  a 
solvent  for  the  alumina  into  the  saline  slag  which  accompanies 
the  aluminium  at  the  moment  of  its  formation.  At  first,  we 
found  it  an  improvement  to  condense  the  vapors  of  aluminium 
chloride,  previously  purified  by  iron,  directly  in  sodium  chloride, 
placed  for  this  purpose  in  a  crucible  and  kept  at  a  red  heat. 
We  produced  in  this  way,  from  highly  colored  material,  a  double 
chloride  very  white  and  free  from  moisture,  and  furnishing  on 
reduction  a  metal  of  fine  appearance.  We  then  introduced 
fluorspar  (CaF^)  into  the  composition  of  the  mixture  to  be 
reduced,  and  we  obtained  good  results  with  the  following  pro- 
portions : 

Aluminium-sodium  chloride 400  grammes. 

Sodium  chloride 200  " 

Calcium  fluoride 200         " 

Sodium 75  to  80  " 


"  The  double  chloride  ought  to  be  melted  and  heated  almost 
to  low  red  heat  at  the  moment  it  is  employed,  the  sodium 
chloride  calcined  and  at  a  red  heat  or  melted,  and  the  fluorspar 
pulverized  and  well  dried.  The  double  chldride,  sodium  chlor- 
ide and  calcium  fluoride  are  mixed  and  alternated  in  layers  in 
the  crucible  with  sodium.  The  top  layer  is  of  the  mixture,  and 
the  cover  is  sodium  chloride.  Heat  gently,  at  first,  until  the 
reaction  ends,  and  then  to  a  heat  about  sufficient  to  melt  silver. 
The  crucible,  or  at  least  that  part  of  it  which  contains  the  mix- 
ture, ought  to  be  of  a  uniform  red  tint,  and  the  material  per- 
fectly liquid.  It  is  stirred  a  long  time  and  cast  on  a  well  dried, 
chalked  plate.  There  flows  out  first  a  very  limpid  liquid,  col- 
orless and  very  fluid ;  then  a  gray  material,  a  little  more  pasty, 
which  contains  aluminium  in  little  grains,  and  is  set  aside ;  and 
finally  a  button  with  small,  metallic  masses  which  of  them- 
selves ought  to  weigh  20  grms.  if  the  operation  has  succeeded 
well.  On  pulverizing  and  sieving  the  gray  slag,  5  or  6  grms. 
of  small  globules  are  obtained,  which  may  be  pressed  together 
by  an  earthen  rod  in  an  ordinary  crucible  heated  to  redness. 
The  globules  are  thus  reunited,  and  when  a  sufficient  quantity 
is  collected  the  metal  is  cast  into  ingots.  In  a  well-conducted 
operation,  75  grms.  of  sodium  ought  to  give  a  button  of  20 
grms.  and  S  grms.  in  grains,  making  a  return  of  one  part  alu- 
minium from  three  of  sodium.  Theory  indicates  one  to  two 
and  a  half,  or  30  grms.  of  aluminium  from  75  of  sodium.  But 
all  the  efforts  which  have  been  made  to  recover  from  the  inso- 
luble slag  the  4  or  5  grms.  of  metal  not  united,  but  easily  vis- 
ible with  a  glass,  have  been  so  far  unsuccessful.  There  is, 
without  doubt,  a  knack,  a  particular  manipulation,  on  which  de- 
pends the  success  of  an  operation  which  would  render  the 
theoretical  amount  of  metal,  but  we  lack  it  yet.  These  opera- 
tions take  place,  in  general,  with  more  facility  on  a  large  scale, 
so  that  we  may  consider  fluorspar  as  being  suitable  for  serving 
in  the  manufacture  of  aluminium  in  crucibles.  We  employed 
very  pure  fluorspar,  and  our  metal  was  quite  exempt  from 
silicon.     It  is  true  that  we  took  a  precaution  which  is  necessary 


to  adopt  in  operations  of  this  kind ;  we  plastered  our  crucibles 
inside  with  a  layer  of  aluminous  paste,  the  composition  of 
which  has  been  given  in  'Ann.  de  Chim.  et  de  Phys.'  xlvi.  195. 
This  paste  is  made  of  calcined  alumina  and  an  aluminate  of 
lime,  the  latter  obtained  by  heating  together  equal  parts  of 
chalk  and  alumina  to  a  high  heat.  By  taking  about  four  parts 
calcined  alumina  and  one  of  aluminate  of  lime  well  pulverized 
and  sieved,  moistening  with  a  little  water,  there  is  obtained  a 
paste  with  which  the  inside  of  an  earthen  crucible  is  quickly 
and  easily  coated.  The  paste  is  spread  evenly  with  a  porcelain 
spatula,  and  compressed  strongly  until  its  surface  has  become 
well  polished.  It  is  allowed  to  dry,  and  then  heated  to  bright 
redness  to  season  the  coating,  which  does  not  melt,  and  pro- 
tects the  crucible  completely  against  the  action  of  the  alumin- 
ium and  fluorspar.  A  crucible  will  serve  several  times  in  suc- 
cession, provided  that  the  new  material  is  put  in  as  soon  as  the 
previous  charge  is  cast.  The  advantages  of  doing  this  are 
that  the  mixture  and  the  sodium  are  put  into  a  crucible  al- 
ready heated  up,  and  so  lose  less  by  volatilization  because  the 
heating  is  done  more  quickly,  and  the  crucible  is  drier  than  if 
a  new  one  had  been  used  or  than  if  it  had  been  let  cool.  A 
new  crucible  should  be  heated  to  at  least  300°  or  400°  before 
being  used.  The  saline  slag  contains  a  large  quantity  of  cal- 
cium chloride,  which  can  be  washed  away  by  water,  and  an  in- 
soluble material  from  which  aluminium  fluoride  can  be  volatil- 

"  Yet  the  operation  just  described,  which  was  a  great  im- 
provement on  previous  ones,  requires  many  precautions  and  a 
certain  skill  of  manipulation  to  succeed  every  time.  But 
nothing  is  more  easy  or  simple  than  to  substitute  cryolite  for 
the  fluorspar.  Then  the  operation  is  much  easier.  The 
amount  of  metal  produced  is  not  much  larger,  although  the 
button  often  weighs  22  grammes,  yet  if  cryolite  can  only  be  ob- 
tained in  abundance  in  a  continuous  supply,  the  process  which 
I  will  describe  will  become  most  economical.  The  charge  is 
made  up  as  before,  except  introducing  cryolite  for  fluorspar. 


In  one  of  our  operations  we  obtained,  with  -j^  grms.  of  sodium, 
a  button  weighing  22  grms.  and  4  grms.  in  globules,  giving  a 
yield  of  one  part  aluminium  to  two  and  eight-tenths  parts 
sodium,  which  is  very  near  to  that  indicated  by  theory.  The 
metal  obtained  was  of  excellent  quality.  However,  it  con- 
tained a  little  iron  coming  from  the  aluminium  chloride,  which 
had  not  been  purified  perfectly.  But  iron  does  not  injure  the 
properties  of  the  metal  as  copper  does ;  and,  save  a  little  bluish 
coloration,  it  does  not  alter  its  appearance  or  its  resistance  to 
physical  and  chemical  agencies. 

"  After  these  attempts  we  tried  performing  the  reduction  sim- 
ply on  the  bed  of  a  reverberatory  furnace,  relying  on  the  imme- 
diate reaction  of  sodium  on  the  double  chloride  to  use  up  these 
materials  before  they  could  be  perceptibly  wasted  by  the  fur- 
nace gases.  This  condition  was  realized  in  practice  with 
unlooked-for  success.  The  reduction  is  now  made  on  a  some- 
what considerable  scale  at  the  Nanterre  works,  and  never,  since 
commencing  to  operate  in  this  way,  has  a  reduction  failed,  the 
results  obtained  being  always  uniform.  The  furnace  now  used 
has  all  the  relative  dimensions  of  a  soda  furnace.  In  fact, 
almost  the  temperature  of  an  ordinary  soda  furnace  is  required 
that  the  operation  may  succeed  perfectly.  The  absolute  dimen- 
sions of  the  furnace,  however,  may  vary  with  the  quantity  of  alu- 
minium to  be  made  in  one  operation,  and  are  not  limited.  With 
a  bed  of  one  square  metre  surface,  6  to  10  kilos  of  aluminium 
can  be  reduced  at  once ;  and  since  each  operation  lasts  about 
four  hours,  and  the  furnace  may  be  recharged  immediately  after 
emptying  it  of  the  materials  just  treated,  it  is  seen  that,  with  so 
small  a  bed,  60  to  lOO  kilos  of  aluminium  can  be  made  in 
twenty-four  hours  without  any  difficulty.  In  this  respect,  I 
think  the  industrial  problem  perfectly  solved.  The  proportions 
which  we  employed  at  first  were — 

Aluminium-sodium  chloride  (crushed) 10  parts. 

Fluorspar 5     " 

Sodium  (in  ingots) 2    " 

"  As  aluminium   is  still  very  dear,  it  is  necessary  to  direct 


great  attention  to  the  return  from  the  materials  used,  and  on 
this  point  there  is  yet  much  progress  to  be  made.  We  ascer- 
tained many  times  that  the  return  was  always  a  little  better,  and 
the  reunion  of  the  metal  to  a  single  ingot  a  little  easier,  when 
cryolite  was  substituted  for  fluorspar,  the  price  of  the  former, 
after  having  been  high,  being  now  lowered  to  350  francs  per 
tonne  (about  $75  per  long  ton).  For  this  reason  we  can  now 
use  cryolite  instead  of  fluorspar,  and  in  the  same  proportions. 
We  can  also  recover  alumina  from  this  cryolite  by  treating  the 
slags  (see  p.  148).  The  double  chloride  and  pulverized  cryo- 
lite are  now  mixed  with  the  sodium  in  small  ingots,  and  the 
mixture  thrown  on  to  the  bed  of  the  heated-up  furnace.  The 
dampers  are  then  shut,  to  prevent  as  much  as  possible  access 
of  air.  Very  soon  a  lively  reaction  begins,  with  the  production 
of  such  heat  that  the  brick  sides  of  the  furnace,  as  well  as  the 
materials  on  the  hearth,  are  made  bright  red-hot.  At  this  heat 
the  mixture  is  almost  completely  fused.  Then  it  is  necessary 
to  open  the  damper  and  direct  the  flame  on  the  bed  in  such 
manner  as  to  heat  the  bath  equally  all  over  and  unite  the  re- 
duced aluminium.  When  the  operation  is  considered  ended,  a 
casting  is  made  by  an  opening  in  the  back  of  the  furnace  and 
the  slag  is  received  in  cast-iron  pots.  At  the  end  of  the  cast 
the  aluminium  arrives  in  a  single  jet,  which  unites  into  a  single 
lump  at  the  bottom  of  the  still-liquid  slag.  The  gray  slag  flow- 
ing out  last  should  be  pulverized  and  sieved,  to  extract  the 
divided  globules  of  aluminium,  200  to  300  grammes  of  which 
can  sometimes  be  extracted  from  one  kilo  of  gray  slag.  The 
pulverization  of  the  slag  is  in  all  cases  indispensable  in  its  sub- 
sequent treatment  for  extracting  its  alumina.  The  slag  is  of 
two  kinds,  one  fluid  and  light,  which  covered  the  bath,  and  is 
rich  in  sodium  chloride ;  the  other  less  fusible  and  pasty,  gray 
in  color,  which  is  more  dense  and  lies  in  contact  with  the  alu- 
minium. The  coloring  material  producing  the  grayness  is  car- 
bon, coming  either  from  the  sodium  or  from  the  oil  which  im- 
pregnated it,  or  finally  from  the  vapor  of  the  oil.  I  attribute 
the  slight  pastiness  of  this  slag  to  a  little  alumina  dissolved  by 
the  fluorides.     This  slag  contains  about: 


Sodium  chloride 60  parts. 

Aluminium  fluoride 40     " 

and  on  washing  it  the  former  dissolves  while  the  latter  remains, 
mixed  with  a  little  cryolite  or  alumina.  This  is  the  alumina 
which  had  been  dissolved  or  retained  in  the  bath  of  fluoride. 
It  will  be  remarked  that  the  bath  of  slag  contains  no  other 
fluoride  than  aluminium  fluoride,  which  does  not  attack  earthen 
crucibles  or  siliceous  materials  in  general  except  at  a  very  high 
temperature.  It  is  for  this  reason  that  the  hearth  and  other  parts 
of  the  furnace  resist  easily  a  fluoride  slag  containing  only  alu- 
minium fluoride,  which  has  not  the  property  of  combining  with 
silicon  fluoride  at  the  expense  of  the  silica  of  the  bricks — as 
sodium  fluoride  does  in  like  circumstances.  In  our  operations, 
cryolite  is  used  only  as  a  flux.  In  the  process  of  reduction 
based  on  cryolite  alone,  the  sodium  fluoride  resulting  is,  on  the 
contrary,  very  dangerous  to  crucibles,  and  it  is  due  to  that  fact 
especially  that  the  aluminium  absorbs  a  large  quantity  of 
silicon,  which  always  happens  with  this  method.  In  fact,  it  is 
well  known  that  metallic  silicon  can  be  prepared  in  this  way  by 
prolonging  the  operation  a  little." 

Deville  closes  his  account  of  the  aluminium  industry  in  1859 
with  these  words :  "  Many  things  yet  remain  to  us  to  do,  and 
we  can  scarcely  say  now  that  we  know  the  true  qualities  of  the 
substances  we  employ.  But  the  matter  is  so  new,  is  harassed 
with  so  many  difiSculties  even  after  all  that  has  been  done,  that 
our  young  enterprise  may  hope  everything  from  the  future  when 
it  shall  have  acquired  experience.  I  ought  to  say,  however, 
that  the  aluminium  industry  is  now  at  such  a  point  that  if  the 
uses  of  the  metal  are  rapidly  extended  it  may  change  its  aspect 
with  great  rapidity.  One  may  ask  to-day  how  much  a  kilo  of 
iron  would  cost  if  a  works  made  only  60  to  100  kilos  of  it  a 
month,  if  large  apparatus  were  excluded  from  this  industry,  and 
iron  obtained  by  laboratory  processes  which  would  permit  it  to 
become  useful  only  by  tedious  after-treatment.  Such  will  not 
be  the  case  with  aluminium,  at  least  with  the  processes  just  de- 
scribed.    In  fact  in  all  I  undertook,  either  alone  or  with  my 


friends,  I  have  always  been  guided  by  this  thought — that  we 
ought  to  adopt  only  such  apparatus  as  is  susceptible  of  being 
immediately  enlarged,  and  to  use  only  materials  almost  as  com- 
mon as  clay  itself  for  the  source  of  the  aluminium." 

The  Deville  Process  (1882). 

The  process  just  described  reached  a  fair  degree  of  perfec- 
tion at  Nanterre,  under  the  direction  of  M.  Paul  Morin.  After- 
wards, some  of  the  chemical  operations  incidental  to  the 
process  were  carried  on  at  the  works  of  the  Chemical  Manufac- 
turing Company  of  Alais  and  Carmargue,  at  Salindres  (Gard), 
owned  by  H.  Merle  &  Co.  At  a  later  date  the  whole  manufac- 
ture was  removed  to  this  place,  while  the  Societe  Anonyme  de 
1' Aluminium,  at  Nanterre,  worked  up  the  metal,  and  placed  it 
on  the  market.  The  Salindres  works,  about  1880,  went  under 
the  management  of  A.  R.  Pechiney  &  Co.,  and  under  the  per- 
sonal attention  of  M.  Pechiney,  the  Deville  process  reached  its 
perfection.  The  following  account  is  taken  mostly  from  M. 
Margottet's  article  on  aluminium  in  Fremy's  Encyclopedic 

An  outline  of  the  process,  as  it  was  prepared,  may  very 
appropriately  be  given  at  this  place,  although  detailed  descrip- 
tions of  the  preliminary  processes  for  preparing  the  materials 
for  reduction  are  given  under  the  appropriate  headings  (see 
pp.  137,  154,  190). 

The  primary  material  to  furnish  the  aluminium  is  bauxite. 
To  obtain  the  metal  it  is  necessary  to  proceed  successively 
through  the  following  operations:  — 

I.  Preparation  of  the  aluminate  of  soda,  and  solution  of  this 
salt  to  separate  it  from  the  ferric  oxide  contained  in  the 

II.  Precipitation  of  hydrated  alumina  from  the  aluminate  of 
soda  by  a  current  of  carbon  dioxide ;   washing  the  precipitate. 

III.  Preparation  of  a  mixture  of  alumina,  carbon,  and  salt, 
drying  it,  and  then  treating  with  gaseous  chlorine  to  obtain  the 
double  chloride  of  aluminium  and  sodium. 


IV.  Lastly,  treatment  of  this  chloride  by  sodium  to  obtain 

The  principal  chemical  reactions  on  which  this  process  rests 
are  the  following: — 

Formation  of  aluminate  of  soda  by  calcining  bauxite  with 
sodium  carbonate — 

(AlFe)  A.2H,0  +  3Na,C03=-Al,03-3Na,0  +  Fe.Oa 
+  2H,0  +  3CO,. 

Formation  of  alumina  by  precipitating  the  aluminate  of  soda 
with  a  current  of  carbon  dioxide — 

Al,03-3Na,0  +  3CO,  +  3H,0  =  Al.Os.sH.O  +  3Na,C03. 

Formation  of  aluminium-sodium  chloride  by  the  action  of 
chlorine  on  a  mixture  of  alumina,  carbon,  and  sodium  chloride — 

AI2O3  +  3C  +  2NaCl  +  6C1  =  2  (AlCla.NaCl)  +  3CO. 

Reduction  of  this  double  chloride  by  sodium — 

AlCIs.NaCl  +  3Na  =  Al  +  4NaCl. 

As  observed  before,  we  will  here  consider  only  the  last  oper- 
ation. The  advances  made  since  1859  are  mostly  in  matters  of 
detail,  which  every  one  knows  are  generally  the  most  import- 
ant part  of  a  process ;  and  so,  although  a  few  of  the  details 
may  be  repeated,  yet  we  think  it  best  not  to  break  the  contin- 
uity of  this  description  by  excising  those  few  sentences  which 
are  nearly  identical  in  the  two  accounts. 

The  difiSculty  of  this  operation,  at  least  from  an  industrial 
point  of  view,  is  to  get  a  slag  fusible  enough  and  light  enough 
to  let  the  reduced  metal  easily  sink  through  it  and  unite. 
This  result  has  been  reached  by  using  cryolite.  This  material 
iorms  with  the  sodium  chloride  resulting  from  the  reaction  a 
very  fusible  slag,  in  the  midst  of  which  the  aluminium  collects 
well,  and  falls  to  the  bottom.  In  one  operation  the  charge  is 
now  composed  of — 


100  kilos Aluminium-sodium  chloride. 

45     "       Cryolite. 

35     "      Sodium. 

The  double  chloride  and  cryolite  are  pulverized,  the  sodium^ 
cut  into  small  pieces  a  little  larger  than  the  thumb,  is  divided 
into  three  equal  parts,  each  part  being  put  into  a  sheet-iron 
basket.  The  mixture  of  double  chloride  and  cryolite,  being 
pulverized,  is  divided  into  four  equal  parts,  three  of  these  are 
respectively  put  in  each  basket  with  the  sodium,  the  fourth 
being  placed  in  a  basket  by  itself.     The  reduction  furnace  (see 

Fig.  25. 



Fig.  25)  is  a  little  furnace  of  refractory  brick,  with  an  inclined 
hearth  and  a  vaulted  roof.  This  furnace  is  strongly  braced  by 
iron  tie-rods,  because  of  the  concussions  caused  by  the  reac- 
tion. The  flame  may  at  any  given  moment  be  directed  into  a. 
flue  outside  of  the  hearth.  At  the  back  part  of  the  furnace,, 
that  is  to  say,  on  that  side  towards  which  the  bed  slopes,  is  a 
little  brick  wah  which  is  built  up  for  each  reduction  and  is. 
taken  away  in  operating  the  running  out  of  the  metal  and  slag> 
A  gutter  of  cast-iron  is  placed  immediately  in  front  of  the  wall 
to  facilitate  running  out  the  materials.  All  this  side  of  the  fur- 
nace ought  to  be  opened  or  closed  at  pleasure  by  means  of  a 
damper.  Lastly,  there  is  an  opening  for  charging  in  the  roof, 
closed  by  a  lid.  At  the  time  of  an  operation  the  furnace 
should  be  heated   to  low  redness,  then  are  introduced  in  rapid 


succession  the  contents  of  the  three  baskets  containing  sodium, 
etc.,  and  lastly  the  fourth  containing  only  double  chloride  and 
no  sodium.  Then  all  the  openings  of  the  furnace  are  closed, 
and  a  very  vivid  reaction  accompanied  by  dull  concussions  im- 
mediately takes  place.  At  the  end  of  fifteen  minutes,  the  ac- 
tion subsides,  the  dampers  are  opened  and  the  heat  continued, 
meanwhile  stirring  the  mass  from  time  to  time  with  an  iron 
poker.  At  the  end  of  three  hours  the  reduction  is  ended,  and 
the  metal  collects  at  the  bottom  of  the  liquid  bath.  Then  the 
running  out  is  proceeded  with  in  three  phases :  First — Running 
off  the  upper  part  of  the  bath,  which  consists  of  a  fluid  material 
completely  free  from  reduced  aluminium  and  constituting  the 
white  slag.  To  run  this  out  a  brick  is  taken  away  from  the 
upper  course  of  the  little  wall  which  terminates  the  hearth. 
These  slags  are  received  in  an  iron  wagon.  Second — Running 
out  the  aluminium.  This  is  done  by  opening  a  small  orifice 
left  in  the  bottom  of  the  brick  wall,  which  was  temporarily 
plugged  up.  The  liquid  metal  is  received  in  a  cast-iron  melt- 
ing pot,  the  bottom  of  which  has  been  previously  heated  to 
redness.  The  aluminium  is  immediately  cast  in  a  series  of 
small  rectangular  cast-iron  moulds.  Third — Running  out  of 
the  rest  of  the  bath,  which  constitutes  the  gray  slags.  These 
were,  like  the  white  slags,  formed  by  the  sodium  chloride  and 
cryolite,  but  they  contain,  in  addition,  isolated  globules  of  alu- 
minium. To  run  these  out,  all  the  bricks  of  the  little  wall  are 
taken  away.. ,  This  slag  is  received  in  the  same  melting  pot  into 
which  the  aluminium  was  run,  the  latter  having  been  already 
moulded.  Here  it  cools  gradually,  and  after  cooling  there  are 
always  found  at  the  bottom  of  the  pot  several  grains  of  metal. 
In  a  good  operation  there  are  taken  from  one  casting  10.5 
kilos  of  aluminium,  which  is  sold  directly  as  commercial  metal. 

The  following  data  as  to  the  expense  of  this  process  may  be 
very  appropriately  inserted  here,  giving  the  cost  at  Salindres  in 
1873,  in  which  year  3600  kilos  are  said  to  have  been  made. 

*  Manufacture  of  one  kilo  of  aluminium. 

*  A.  Wurtz,  Wagner's  Jahresb.,  1874,  vol.  xxi. 


Sodium 3.44  kilos  @  11.32  fr.  per  kilo  =  38  fr.  90  cent. 


chloride.  . . .   10.04       "  2.48      "        "  =  24  "  90  " 

Cryolite 3.87        "        61.0        "       100  kilos  ^    2  "  36  " 

Coal 29.17        "  1.40       "  "         =    o  "  41  " 

Wages I  "  80  " 

Costs o  "  88  " 

Total 69  "  25     " 

This  must  be  increased  ten  per  cent,  for  losses  and  other  ex- 
penses, making  the  cost  of  aluminium  80  fr.  per  kilo,  and  it  is 
sold  for  100.      ($9.00  per  lb.) 

According  to  a  statement  in  the  '  Bull,  de  la  Soc.  de  I'lndustrie 
Minerale,'  ii.  451,  made  in  1882,  Salindres  was  then  the  only 
place  in  which  aluminium  was  being  manufactured.  The 
Deville  process  was  finally  driven  out  of  the  market,  and  the 
manufacture  at  Salindres  suspended,  in  1890. 

Niewerth's  Process  (1883). 

This  method  can  be  regarded  as  little  more  than  a  suggestion, 
since  it  follows  exactly  the  lines  of  some  of  Deville's  earlier  ex- 
periments. Although  theoretically  very  advantageous,  yet  in 
practice  it  has  probably  been  found  far  inferior  in  point  of  yield 
of  metal  and  expense  to  the  ordinary  sodium  processes.  The 
patent  is  taken  out  in  the  United  States  and  other  countries  in 
the  name  of  H.  Niewerth,  of  Hanover,  and  is  thus  summarized  : 

*A  compound  of  aluminium,  with  chlorine  or  fluorine,  is 
brought  by  any  means  into  the  form  of  vapor,  and  conducted, 
strongly  heated,  into  contact  with  a  mixture  of  62  parts  sodium 
carbonate,  28  coal,  and  10  chalk,  which  is  also  in  a  highly  heated 
condition.  This  mixture  disengages  sodium,  which  reduces  the 
gaseous  chloride  or  fluoride  of  aluminium,  the  nascent  sodium 
being  the  reducing  agent.  In  place  of  the  above  mixture  other 
suitable  mixtures  which  generate  sodium  may  be  employed,  or 
mixtures  may  also  advantageously  be  used  from  which  potassium 
is  generated. 

*  Sci.  Am.  Supple.,  Nov.  17,  1883. 


Gadsden's  Patent  (1883). 

H.  A.  Gadsden,  of  London,  and  E.  Foote,*  of  New  York, 
were  granted  a  patent  based  on  the  principle  of  heating  in  a 
retort  sodium  carbonate  and  carbonaceous  matter,  or  any  suit- 
able mixture  for  generating  sodium,  and  conducting  the  vapor 
of  sodium  produced  into  another  retort,  lined  with  carbon,  in 
which  aluminium  chloride,  or  aluminium-sodium  chloride  or 
cryolite,  has  been  placed  and  heated.  The  second  English  pat- 
ent claims  to  heat  a  mixture  which  will  generate  sodium  in  one 
retort,  and  pass  chlorine  over  a  mixture  of  carbon  and  alum- 
ina, thus  generating  aluminium  chloride,  in  another  retort,  and 
then  mixing  the  two  vapors  in  a  third  retort  or  reaction 

Friskmuth's  Process  (1884). 

This  was  patented  in  the  United  States  in  1884  (U.  S.  Pat. 
308,152,  Nov.  1884).  In  what  the  originality  of  the  process 
consists,  in  view  of  Deville's  publications  and  even  in  view  of 
the  processes  just  mentioned,  we  cannot  see.  Col.  Frishmuth 
himself  admitted,  in  1887,  having  abandoned  the  sodium  process, 
as  the  difficulties  of  the  method  did  not  permit  its  competing 
with  the  more  roundabout  but  more  easily-conducted  operation 
with  solid  sodium.  A  simple  transcript  of  the  claims  in  his 
patent  will  give  a  sufficiently  extended  idea  of  the  reactions 
proposed  to  be  used. 

1.  The  simultaneous  generation  of  sodium  vapor  and  a  vola- 
tile compound  of  aluminium  in  two  separate  vessels  or  retorts, 
and  mingling  the  vapors  thus  obtained  in  a  nascent  (  !  )  state 
in  a  third  vessel,  wherein  they  react  on  each  other. 

2.  The  sodium  vapor  is  produced  from  a  mixture  of  a  sodium 
compound  and  carbon,  or  some  other  reducing  agent;  and  the 
aluminous  vapor  from  aluminous  material. 

3.  The  simultaneous  generation  of  sodium  vapor  and  vapor 
of  aluminium  chloride  or  aluminium  fluoride;  or  of  sodium 
vapor  and  aluminium-sodium  chloride. 

*  English  patents  1995  and  493°  (1883);  German  patent  27,572  (1884). 

2  70  ALUMINIUM. 

4.  Converting  the  aluminous  material  to  a  vapor  by  heating 
it  in  a  retort  with  sodium  chloride,  and  subjecting  it  at  the 
same  time  to  chlorine  gas ;  mingling  the  vapor  of  aluminium- 
sodium  chloride  thus  obtained  with  vapor  simultaneously  gen- 
erated from  sodium  carbonate  and  carbon. 

H.  von  Grousillier' s  Improvement  (1885)- 

This  suggestion  as  to  the  way  of  performing  the  reduction 
by  sodium  is  the  subject  of  the  English  patent  7858,  June  29, 
18B5.  Dr.  Fischer  remarks  on  it,  in  "  Wagner's  Jahresbericht" 
for  1885,  that  "it  is  apparently  wholly  worked  out  at  the 
writing-table,"  The  patentee.  Hector  von  Grousillier,  Springe, 
Hanover,  thus  describes  his  invention : 

"  In  order  to  avoid  the  difficulties  ordinarily  met  with  in  the 
use  of  aluminium-sodium  chloride  to  obtain  aluminium,  I  raise 
the  volatilizing  point  of  aluminium  chloride  by  performing  its 
reduction,  either  chemically  or  electrolytically,  under  pressure 
in  a  strong  hermetically-closed  vessel,  lined  with  clay  or  mag- 
nesia, and  provided  with  a  safety  valve." 

The  Deville-Castner  Process  (1886). 

This  last  development  of  the  old  Deville  process  was  ope- 
rated by  the  Aluminium  Company,  Limited,  at  their  large  new 
works  at  Oldbury,  near  Birmingham,  England.  The  plant 
covered  nearly  five  acres  of  ground,  and  adjoined  Chance  Bros.' 
large  chemical  works,  from  which  the  hydrochloric  acid  used 
was  obtained  and  the  waste  soda-liquors  returned,  by  means  of 
large  pipes  connecting  the  two  plants.  The  company  was  thus 
in  position  to  obtain  acid  and  dispose  of  its  by-products  to 
very  good  advantage.  The  principle  on  which  the  process  was 
worked  is  similar  to  its  predecessor,  in  being  the  reduction  of 
aluminium-sodium  chloride  by  sodium,  but  it  improves  on  the 
other  in  the  cheaper  production  of  both  these  materials.  For 
instance,  the  alumina  used  is  obtained  and  converted  into 
double  chloride  by  Mr.  Webster's  processes,  by  which  the  cost 
of  this  salt  is  not  over  3^.  per  lb.  (see  p.  164),  as  against  i2d.. 


the  cost  at  Salindres ;  further,  by  Mr.  Castner's  sodium  process 
it  is  acknowledged  that  the  sodium  cost  only  about  ^d.  per  lb., 
as  against  48^^.,  or  $1,  as  formerly.  Since  10  lbs.  of  the  chlo- 
ride and  3  lbs.  of  sodium  are  required  to  produce  i  lb.  of  alu- 
minium, the  average  saving  in  these  two  items,  over  the  old 
process,  is  somewhere  about  75  per  cent. 

The  works  contain  a  sodium  building,  in  which  are  four  large 
sodium  furnaces,  each  capable  of  producing  over  500  lbs.  of 
that  metal  in  twenty-four  hours ;  the  sodium  is  also  remelted 
and  stored  in  the  same  building  (see  p.  215).  The  double 
chloride  furnaces  are  in  a  building  250  feet  by  50  feet  wide,  there 
being  12  furnaces,  each  containing  5  retorts.  The  total  output 
of  double  chloride  is  an  average  of  5000  lbs.  per  day.  (See.  p. 
162).  Connected  with  this  building  is  a  chlorine  plant  of  the 
largest  size,  capable  of  supplying  about  a  ton  and  a  half  of 
chlorine  a  day.  In  a  separate  building  are  two  reverberatory 
furnaces,  in  which  the  final  reduction  takes  place  and  the  alu- 
minium is  produced.  Besides  these  there  are  a  rolling  mill, 
wire  mill,  and  foundry  on  the  grounds.  From  the  quantity  of 
sodium  and  double  chloride  produced,  we  can  see  that  the 
works  can  produce  about  500  lbs.  of  aluminium  a  day,  or 
150,000  lbs.  a  year,  with  some  sodium  left  over  for  sale  or  other 

The  mode  of  conducting  the  reduction  is  not  very  different 
from  that  practiced  at  Salindres.  There  are  two  regenerative 
reverberatory  furnaces  used,  one  about  twice  as  large  as  the 
other.  The  larger  furnace  has  a  bed  about  six  feet  square,  slop- 
ing towards  the  front  of  the  furnace,  through  which  are  several 
openings  at  different  heights.  The  charge  for  this  furnace  con- 
sists of  1200  lbs.  of  double  chloride,  350  lbs.  of  sodium,  and 
600  lbs.  of  cryolite  for  a  flux.  The  chloride  is  in  small  pieces, 
the  cryolite  is  in  powder,  and  the  sodium  is  cut  into  thin  slices 
by  a  machine.  These  ingredients  are  put  into  a  revolving 
wooden  drum  placed  on  a  staging  over  the  furnace,  and  are 
there  thoroughly  mixed.  The  drum  is  then  opened  and 
turned,  when  the  contents  fall  into    a    small  wagon  beneath. 


The  furnace  having  been  raised  to  the  required  temperature,  all 
the  dampers  are  shut  and  the  car  is  moved  on  a  track  immedi- 
ately over  a. large  hopper  placed  in  the  roof  of  the  furnace. 
The  hopper  being  opened,  the  charge  is  dumped  in  and  drops 
on  to  the  centre  of  the  hearth.  The  reaction  is  immediate, 
and  the  whole  charge  becomes  liquid  in  a  very  short  time. 
After  a  few  minutes,  heating  gas  is  again  turned  on,  and  the 
furnace  kept  moderately  hot  for  two  or  three  hours.  The  reac- 
tion has  been 

AlCla.NaCl  +  3Na  =  Al  +  4NaCl 

and  the  aluminium  gathers  under  the  bath  of  cryolite  and  sod- 
ium chloride.  One  of  the  lower  tap-holes  is  then  opened  with 
a  bar,  and  the  aluminium  run  out  into  moulds.  When  the 
metal  has  all  run  out  it  is  followed  by  slag,  which  flows  into 
iron  wagons.  The  openings  are  then  plugged  up  and  the  fur- 
nace is  ready  for  another  charge.  The  charge  given  produces 
usually  115  to  120  lbs.  of  aluminium,  the  whole  operation  last- 
ing about  4  hours.  The  large  furnace  could  thus  produce  840- 
lbs.  in  24  hours,  and  the  smaller  one  half  that  quantity.  The 
first  portion  of  metal  running  out  is  the  purest,  the  latter  por- 
tions, and  especially  that  entangled  in  the  slag  on  the  hearth,  and 
which  has  to  be  scraped  out,  containing  more  foreign  sub- 
stances. This  impure  metal  is  about  one-fourth  of  all  the 
aluminium  in  the  charge. 

The  purity  of  the  metal  run  out  depends  directly  on  the 
purity  of  the  chloride  used.  If  the  double  chloride  contains 
0.2  per  cent,  of  iron,  the  metal  produced  will  very  probably 
contain  all  of  it,  or  2  per  cent.  Using  the  double  chloride 
purified  by  Mr.  Castner's  new  method  (see  p.  163),  by  which 
the  content  of  iron  is  reduced  to  0.05  per  cent,  or  less,  alu- 
minium can  be  made  containing  less  than  0.5  per  cent,  of  iron 
and  from  99  to  99.5  per  cent,  of  aluminium.  Professor  Roscoe 
exhibited  at  one  of  his  lectures  a  mass  of  metal  weighing  116' 
lbs.,  being  one  single  running  from  the  furnace,  and  which  con- 
tained only  0.3  per  cent,  of  silicon  and  0.5  per  cent.  iron.     In. 


practice,  the  metal  from  8  or  10  runnings  is  melted  down   to- 
gether to  make  a  uniform  quality. 

Taking  the  figures  given,  it  appears  that  the  metal  run  out 
represents  70  per  cent,  of  the  aluminium  in  the  charge,  and  80 
percent,  of  the  weight  which  the  sodium  put  in  should  reduce; 
but  since  an  indeterminate  weight  is  sifted  and  picked  from  the 
slag,  it  is  probable  that  the  utilization  of  the  materials  is  more 
perfect  than  the  above  percentages.  However,  this  seems  to 
be  the  part  of  the  old  Deville  process  least  improved  upon  in 
these  new  works,  for  there  seems  to  be  plenty  of  room  for  im- 
provement in  perfecting  the  utilization  of  materials,  especially 
in  regard  to  loss  of  sodium  by  volatilization,  which  undoubt- 
edly takes  place  and  which  can  possibly  be  altogether  pre- 

The  above  description,  written  in  1890,  was  followed  only 
one  year  later  by  the  closing  of  this  splendid  works.  The  very 
lowest  point  to  which  the  Deville-Castner  process  could  reduce 
the  cost  of  producing  aluminium  was  between  4  and  S  shillings 
per  pound ;  and  when  the  metal  was  put  on  the  market  by  users 
of  the  electrolytic  process  at  $1.50  per  pound,  in  1891,  there 
was  nothing  left  for  the  sodium  process  except  to  give  up  the 
business.  The  company,  however,  continues  to  run  the  works, 
making  and  selling  large  quantities  of  sodium. 


POTASSIUM  OR  SODIUM  {Continued). 


Methods  based  on  the  reduction  of  cryolite. 
These  can  be   most  conveniently  presented  in  chronological 

Rose's  Experiments  (1855). 

We  will  here  give  H.  Rose's  entire  paper,  as  an  account  of 
this  eminent  chemist's  investigations  written  out  by  himself 
with  great  detail,  describing  failures  as  well  as  successes, 
cannot  but  be  of  value  to  all  interested  in  the  production  of 

"  Since  the  discovery  of  aluminium  by  Wohler,  Deville  has 
recently  devised  the  means  of  procuring  the  metal  in  large,  solid 
masses,  in  which  condition  it  exhibits  properties  with  which  we 
were  previously  unacquainted  in  its  more  pulverulent  form  as 
procured  by  Wohler's  method.  While,  for  instance,  in  the  lat- 
ter state  it  burns  vividly  to  white  earthy  alumina  on  being  ig- 
nited, the  fused  globules  may  be  heated  to  redness  without 
perceptibly  oxidizing.  These  differences  may  be  ascribed  to 
the  greater  amount  of  division  on  the  one  hand  and  of  density 
on  the  other.  According  to  Deville,  however,  Wohler's  metal 
contains  platinum,  by  which  he  explains  its  difficulty  of  fusion, 
although  it  affords  white  alumina  by  combustion.  Upon  the 
publication  of  Deville's  researches,  I  also  tried  to  produce 
aluminium  by  the  decomposition  of  aluminium-sodium  chloride 
by  means  of  sodium.     I  did  not,  however,  obtain  satisfactory 

*  Pogg.  Annalen,  Sept.,  1855. 


results.  Moreover,  Prof.  Rammelsberg,  who  followed  exactly 
the  method  of  Deville,  obtained  but  a  very  small  product,  and 
found  it  very  difficult  to  prevent  the  cracking  of  the  glass  tube 
in  which  the  experiment  was  conducted,  by  the  action  of  the 
vapor  of  sodium  on  aluminium  chloride.  It  appeared  to  me 
that  a  great  amount  of  time,  trouble  and  expense,  as  well  as 
long  practice,  was  necessary  to  obtain  even  small  quantities  of 
this  remarkable  metal. 

"  The  employment  of  aluminium  chloride  and  its  compounds 
with  alkali  chlorides  is  particularly  inconvenient,  owing  to  their 
volatility,  deliquescence,  and  to  the  necessity  of  preventing  all 
access  of  air  during  their  treatment  with  sodium.  It  very  soon 
occurred  to  me  that  it  would  be  better  to  use  the  fluoride  of 
aluminium  instead  of  the  chloride ;  or  rather  the  combination 
of  the  fluoride  with  alkaline  fluorides,  such  as  we  know  them 
through  the  investigations  of  Berzelius,  who  pointed  out  the 
strong  affinity  of  aluminium  fluoride  for  sodium  fluoride  and 
potassium  fluoride,  and  that  the  mineral  occurring  in  nature 
under  the  name  of  cryolite  was  a  pure  compound  of  aluminium 
fluoride  and  sodium  fluoride. 

"  This  compound  is  as  well  fitted  for  the  preparation  of 
aluminium  by  means  of  sodium  as  aluminium  chloride  or 
aluminium-sodium  chloride.  Moreover,  as  cryolite  is  not  vola- 
tile, is  readily  reduced  to  the  most  minute  state  of  division,  is 
free  from  water  and  does  not  attract  moisture  from  the  air,  it 
affords  peculiar  advantages  over  the  above-mentioned  com- 
pounds. In  fact,  I  succeeded  with  much  less  trouble  in  pre- 
paring aluminium  by  exposing  cryolite  together  with  sodium 
to  a  strong  red  heat  in  an  iron  crucible,  than  by  using  alu- 
minium chloride  and  its  compounds.  But  the  scarcity  of  cryo- 
lite prevented  my  pursuing  the  experiments.  In  consequence 
of  receiving,  however,  from  Prof.  Krantz,  of  Bonn,  a  consider- 
able quantity  of  the  purest  cryolite  at  a  very  moderate  price 
($2  per  kilo),  I  was  enabled  to  renew  the  investigation. 

"  I  was  particularly  stimulated  by  finding,  most  unexpect- 
edly, that  cryolite  was  to  be  obtained  here  in  Berlin  commer- 


cially  at  an  inconceivably  low  price.  Prof.  Krantz  had  already 
informed  me  that  cryolite  occurred  in  commerce  in  bulk,  but 
could  not  learn  where.  Shortly  after,  M.  Rudel,  the  manager 
of  the  chemical  works  of  H.  Kunheim,  gave  me  a  sample  of  a 
coarse  white  powder,  large  quantities  of  which  were  brought 
from  Greenland  by  way  of  Copenhagen  to  Stettin,  under  the 
name  of  mineral  soda,  and  at  the  price  of  $3  per  centner. 
Samples  had  been  sent  to  the  soap  boilers,  and  a  soda-lye 
had  been  extracted  from  it  by  means  of  quicklime,  especially 
adapted  to  the  preparation  of  many  kinds  of  soap,  probably  from 
its  containing  alumina.  It  is  a  fact,  that  powdered  cryolite  is 
completely  decomposed  by  quicklime  and  water.  The  fluoride 
of  lime  formed  contains  no  alumina,  which  is  all  dissolved  by  the 
caustic  soda  solution ;  and  this,  on  its  side,  is  free  from  fluor- 
ine, or  only  contains  a  minute  trace.  I  found  this  powder  to 
be  of  equal  purity  to  that  received  from  Prof.  Krantz.  It  dis- 
solved without  residue  in  hydrochloric  acid  (in  platinum  ves- 
sels) ;  the  solution  evaporated  to  dryness  with  sulphuric  acid, 
and  heated  till  excess  of  acid  was  dissipated,  gave  a  residue 
which  dissolved  completely  in  water,  with  the  aid  of  a  little 
hydrochloric  acid.  From  this  solution,  ammonia  precipitated 
a  considerable  quantity  of  alumina.  The  solution  filtered  from 
the  precipitate  furnished,  on  evaporation,  a  residue  of  sulphate 
of  soda,  free  from  potash.  Moreover,  the  powder  gave  the 
well-known  reactions  of  fluorine  in  a  marked  degree.  This 
powder  was  cryolite  of  great  purity :  therefore  the  coarse  pow- 
der I  first  obtained  was  not  the  form  in  which  it  was  originally 
produced.  It  is  now  obtainable  in  Berlin  in  great  masses ;  for 
the  preparation  of  aluminium  it  must,  however,  be  reduced  to  a 
very  fine  powder. 

"  In  my  experiments  on  the  preparatipn  of  aluminium,  which 
were  performed  in  company  with  M.  Weber,  and  with  his  most 
zealous  assistance,  I  made  use  of  small  iron  crucibles,  i  ^ 
inches  high  and  i^  inches  upper  diameter,  which  I  had  cast 
here.  In  these  I  placed  the  finely  divided  cryolite  between 
thin  layers  of  sodium,  pressed  it  down  tight,  covered  it  with  a 


good  layer  of  potassium  chloride  (KCl),  and  closed  the  cruc- 
ible with  a  well-fitting  porcelain  cover.  I  found  potassium 
chloride  the  most  advantageous  flux  to  employ ;  it  has  the  low- 
est specific  gravity  of  any  which  could  be  used,  an  important 
point  when  the  slight  density  of  the  metal  is  taken  into  consid- 
eration. It  also  increases  the  fusibility  of  the  sodium  fluoride. 
I  usually  employed  equal  weights  of  cryolite  and  potassium 
chloride,  and  for  every  five  parts  of  cryolite  two  parts  of  so- 
dium. The  most  fitting  quantity  for  the  crucible  was  found  to 
be  ten  grammes  of  powdered  cryolite.  The  whole  was  raised 
to  a  strong  red  heat  by  means  of  a  gas-air  blowpipe.  It  was 
found  most  advantageous  to  maintain  the  heat  for  about  half  an 
hour,  and  not  longer,  the  crucible  being  kept  closely  covered 
the  whole  time ;  the  contents  were  then  found  to  be  well  fused. 
When  quite  cold  the  melted  mass  is  removed  from  the  crucible 
by  means  of  a  spatula ;  this  is  facilitated  by  striking  the  outside 
with  a  hammer.  The  crucible  may  be  employed  several  times, 
at  last  it  is  broken  by  the  hammer  blows.  The  melted  mass  is 
treated  with  water,  when  at  times  only  a  very  minute  evolution 
of  hydrogen  gas  is  observed,  which  has  the  same  unpleasant 
odor  as  the  gas  evolved  during  solution  of  iron  in  hydrochloric 
acid.  The  carbon  contained  in  this  gas  is  derived  from  a  very 
slight  trace  of  naphtha  adhering  to  the  sodium  after  drying  it. 
On  account  of  the  difficult  solubility  of  sodium  fluoride,  the 
mass  is  very  slowly  acted  on  by  water,  although  the  insolubility 
is  somewhat  diminished  by  the  presence  of  the  potassium  chlo- 
ride. After  twelve  hours  the  mass  is  softened  so  far  that  it 
may  be  removed  from  the  liquid  and  broken  down  in  a  porce- 
lain mortar.  Large  globules  of  aluminium  are  then  discovered, 
weighing  from  0.3  to  0.4  or  even  0.5  grammes,  which  may  be 
separated  out.  The  smaller  globules  cannot  well  be  separated 
from  the  undecomposed  cryolite  and  the  alumina  always  pro- 
duced by  washing,  owing  to  their  being  specifically  lighter  than 
the  latter.  The  whole  is  treated  with  nitric  acid  in  the  cold. 
The  alumina  is  not  dissolved  thereby,  but  the  little  globules 
then  first  assume  their  true  metallic  lustre.     They  are  dried  and 


rubbed  on  fine  silk  muslin ;  the  finely  powdered,  undecom- 
posed  cryolite  and  alumina  pass  through,  while  the  globules 
remain  on  the  gauze.  The  mass  should  be  treated  in  a  plati- 
num or  silver  vessel;  a  porcelain  vessel  would  be  powerfully 
acted  on  by  the  sodium  fluoride.  The  solution,  after  standing 
till  clear,  may  be  evaporated  to  dryness  in  a  platinum  capsule, 
in  order  to  obtain  the  sodium  fluoride,  mixed  however  with 
much  potassium  chloride.  The  small  globules  may  be  united 
by  fusion  in  a  small  well-covered  porcelain  crucible,  under  a 
layer  of  potassium  chloride.  They  cannot  be  united  without  a 
flux.  They  cannot  be  united  by  mere  fusion,  like  globules  of 
silver,  for  instance,  for  though  they  do  not  appear  to  oxidize 
on  ignition  in  the  air,  yet  they  become  coated  with  a  scarcely 
perceptible  film  of  oxide,  which  prevents  their  running  together 
into  a  mass.  This  fusion  with  potassium  chloride  is  always  at- 
tended with  a  loss  of  aluminium.  Buttons  weighing  0.85 
gramme  lost,  when  so  treated,  0.05  gramme.  The  potassium 
chloride  when  dissolved  in  water  left  a  small  quantity  of  alu- 
mina undissolved,  but  the  solution  contained  none.  Another 
portion  of  the  metal  had  undoubtedly  decomposed  the  potas- 
sium chloride ;  and  a  portion  of  this  salt  and  aluminium  chlo- 
ride must  have  been  volatilized  during  fusion  (other  metals,  as 
copper  and  silver,  behave  in  a  similar  manner — Pogg.  Ixviii. 
287).  I  therefore  followed  the  instructions  of  Deville,  and 
melted  the  globules  under  a  stratum  of  aluminium-sodium  chlo- 
ride in  a  covered  porcelain  crucible.  The  salt  was  melted  first, 
and 'then  the  globules  of  metal  added  to  the  melted  mass. 
There  is  no  loss,  or  a  very  trifling  one  of  a  few  milligrammes  of 
metal,  by  this  proceeding.  When  the  aluminium  is  fused 
under  potassium  chloride  its  surface  is  not  perfectly  smooth, 
but  exhibits  minute  concavities ;  with  aluminium-sodium  chlo- 
ride this  is  not  the  case.  The  readiest  method  of  preparing 
the  double  chloride  for  this  purpose  is  by  placing  a  mixture  of 
alumina  and  carbon  in  a  glass  tube,  as  wide  as  possible,  and 
inside  this  a  tube  of  less  diameter,  open  at  both  ends,  and  con- 
taining sodium   chloride.     If  the  spot  where  the  mixture  is 


placed  be  very  strongly  heated,  and  that  where  the  sodium 
chloride  is  situated,  more  moderately,  while  a  current  of  chlo- 
rine is  passed  through  the  tube,  the  vapor  of  aluminium  chlo- 
lide  is  so  eagerly  absorbed  by  the  sodium  chloride  that  none 
or  at  most  a  trace  is  deposited  in  any  other  part  of  the  tube. 
If  the  smaller  tube  be  weighed  before  the  operation,  the 
amount  absorbed  is  readily  determined.  It  is  not  uniformly 
combined  with  the  sodium  chloride,  for  that  part  which  is  near- 
est to  the  mixture  of  charcoal  and  alumina  will  be  found  to 
have  absorbed  the  most. 

"  I  have  varied  in  many  ways  the  process  for  the  preparation 
of  aluminium,  but  in  the  end  have  returned  to  the  one  just  de- 
scribed. I  often  placed  the  sodium  in  the  bottom  of  the  cruci- 
ble, the  powdered  cryolite  above  it,  and  the  potassium  chloride 
above  all.  On  proceeding  in  this  manner,  it  was  observed  that 
much  sodium  was  volatilzed,  burning  with  a  strong  yellow 
flame,  which  never  occurred  when  it  was  cut  into  thin  slices  and 
placed  in  alternate  layers  with  the  cryolite,  in  which  case  the 
process  goes  on  quietly.  When  the  crucible  begins  to  get  red 
hot,  the  temperature  suddenly  rises,  owing  to  the  commence- 
ment of  the  decomposition  of  the  compound  ;  no  lowering  of  the 
temperature  should  be  allowed,  but  the  heat  should  be  steadily 
maintained,  not  longer,  however,  than  half  an  hour.  By  pro- 
longing the  process  a  loss  would  be  sustained,  owing  to  the 
action  of  the  potassium  chloride  on  the  aluminium.  Nor  does 
the  size  of  the  globules  increase  on  extending  the  time  even  to 
two  hours :  this  efifect  can  only  be  produced  by  obtaining  the 
highest  possible  temperature.  If  the  process  be  stopped,  how- 
ever, after  five  or  ten  minutes  of  very  strong  heat,  the  produc- 
tion is  very  small,  as  the  metal  has  not  had  sufficient  time 
to  conglomerate  into  globules,  but  is  in  a  pulverulent  form  and 
burns  to  alumina  during  the  cooling  of  the  crucible.  No  ad- 
vantage is  gained  by  mixing  the  cryolite  with  a  portion  of 
chloride  before  placing  it  between  the  layers  of  sodium,  neither 
did  I  increase  the  production  by  using  aluminium  sodium 
chloride  to  cover  the  mixture  instead  of  potassium  chloride.     I 


repeatedly  employed  decrepitated  sodium  chloride  as  a  flux  in  the 
absence  of  potassium  chloride,  without  remarking  any  important 
difference  in  the  amount  of  metal  produced,  although  a  higher 
temperature  is  in  this  case  required.  The  operations  may  also 
be  conducted  in  refractory  unglazed  crucibles  made  of  stone- 
ware, and  of  the  same  dimensions,  although  they  do  not  resist  so 
well  the  action  of  the  sodium  fluoride  at  any  high  heats,  but  fuse 
in  one  or  more  places.  The  iron  crucibles  fuse,  however, 
when  exposed  to  a  very  high  temperature  in  a  charcoal  fire. 
The  product  of  metal  was  found  to  vary  very  much,  even  when 
operating  exactly  in  the  manner  recommended,  and  with  the 
same  quantities  of  materials.  I  never  succeeded  in  reducing  the 
whole  amount  of  metal  contained  in  the  cryolite  (which  con- 
tains 13  per  cent,  of  aluminium).  By  operating  on  10 
grammes  of  cryolite,  the  quantity  I  always  employed  in  the 
small  iron  crucible,  the  most  successful  result  was  0.8  grm.  But 
0.5  or  even  0.4  grm.  may  be  considered  favorable ;  many  times 
I  obtained  only  0.3  grm.,  or  even  less.  These  very  different 
results  depend  on  various  causes,  more  particularly,  however, 
on  the  degree  of  heat  obtained.  The  greater  the  heat,  the 
greater  the  amount  of  large  globules,  and  the  less  amount  of 
minutely  divided  metal  to  oxidize  during  the  cooling  of  the 
crucible.  I  succeeded  once  or  twice  in  reducing  nearly  the 
whole  of  the  metal  to  one  single  button  weighing  0.5  grm.,  at 
a  very  high  heat  in  a  stoneware  crucible.  I  could  not  always 
obtain  the  same  heat  with  the  blowpipe,  as  it  depended  in  some 
degree  on  the  pressure  in  the  gasometer  in  the  gas-works, 
which  varies  at  different  hours  of.  the  day.  The  following  ex- 
periment will  show  how  great  the  loss  of  metal  may  be  owing 
to  oxidation  during  the  slow  cooling  of  the  crucible  and  its  con- 
tents:  In  a  large  iron  crucible  were  placed  35  grms.  of  cryolite 
in  alternate  layers  with  14  grms.  of  sodium,  and  the  whole  cov- 
ered with  a  thick  stratum  of  potassium  chloride.  The  crucible, 
covered  by  a  porcelain  cover,  was  placed  in  a  larger  earthen 
one  also  covered,  and  the  whole  exposed  to  a  good  heat  in  a 
draft  furnace  for  one  hour,  and   cooled  as  slowly  as  possible. 


The  product  in  this  case  was  remarkably  small,  for  O.135  grm. 
of  aluminium  was  all  that  could  be  obtained  in  globules.  The 
differences  in  the  amounts  reduced  depend  also  in  some  degree 
on  the  more  or  less  successful  stratification  of  the  sodium 
with  the  powdered  cryolite,  as  much  of  the  latter  sometimes 
escapes  decomposition.  The  greater  the  amount  of  sodium 
employed,  the  less  likely  is  this  to  be  the  case ;  however,  owing 
to  the  great  difference  in  their  prices,  I  never  employed  more 
than  4  grms.  of  sodium  to  10  grms.  of  cryolite.  In  order  to 
avoid  this  loss  by  oxidation  I  tried  another  method  of  prepara- 
tion :  Twenty  grms.  of  cryolite  were  heated  intensely  in  a  gun- 
barrel  in  a  current  of  hydrogen,  and  then  the  vapor  of  8  grms. 
of  sodium  passed  over  it.  This  was  effected  simply  by  placing 
the  sodium  in  a  little  iron  tray  in  a  part  of  a  gun-barrel  without 
the  fire,  and  pushing  it  forward  when  the  cryolite  had  attained 
a  maximum  temperature.  The  operation  went  on  very  well, 
the  whole  being  allowed  to  cool  in  a  current  of  hydrogen. 
After  the  treatment  with  water,  in  which  the  sodium  fluoride 
dissolved  very  slowly,  I  obtained  a  black  powder  consisting  for 
the  most  part  of  iron.  Its  solution  in  hydrochloric  acid  gave 
small  evidence  of  aluminium.  The  small  amounts  I  obtained, 
however,  should  not  deter  others  from  making  these  experi- 
ments. These  are  the  results  of  first  experiments,  on  which  I 
have  not  been  able  to  expend  much  time.  Now  that  cryolite 
can  be  procured  at  so  moderate  a  price,  and  sodium  by  De- 
ville's  improvements  will  in  future  become  so  much  cheaper,  it 
is  in  the  power  of  every  chemist  to  engage  in  the  preparation  of 
aluminium,  and  I  have  no  doubt  that  in  a  short  time  methods 
M'ill  be  found  affording  a  much  more  profitable  result. 

"  To  conclude,  I  am  of  opinion  that  cryolite  is  the  best 
adapted  of  all  the  compounds  of  aluminium  for  the  preparation 
of  this  metal.  It  deserves  the  preference  over  aluminium-sodium 
chloride  or  aluminium  chloride,  and  it  might  still  be  employed 
with  great  advantage  even  if  its  price  were  to  rise  considerably. 
The  attempts  at  preparing  aluminium  direct  from  alumina  have 
as  yet  been  unattended  with  success.     Potassium  and  sodium 


appear  only  to  reduce  metallic  oxides  when  the  potash  and 
soda  produced  are  capable  of  forming  compounds  with  a  por- 
tion of  the  oxide  remaining  as  such.  Pure  potash  and  soda, 
with  whose  properties  we  are  very  slightly  acquainted,  do  not 
appear  to  be  formed  in  this  case.  Since,  however,  alumina 
combines  so  readily  with  the  alkalies  to  form  aluminates,  one 
would  be  inclined  to  believe  that  the  reduction  of  alumina  by^ 
the  alkali  metals  should  succeed.  But  even  were  it  possible  to^ 
obtain  the  metal  directly  from  alumina,  it  is  very  probable  that 
cryolite  would  long  be  preferred  should  it  remain  at  a  moderate 
price,  for  it  is  furnished  by  nature  in  a  rare  state  of  purity,  and 
the  aluminium  is  combined  in  it  with  sodium  and  fluorine  only, 
which  exercise  no  prejudicial  influence  on  the  properties  of  the 
metal,  whereas  alumina  is  rarely  found  in  nature  in  a  pure  state 
and  in  a  dense,  compact  condition,  and  to  prepare  it  on  a  large 
scale,  freeing  it  from  those  substances  which  would  act  injuri- 
ously on  the  properties  of  the  metal,  would  be  attended  with 
great  difficulty. 

"  The  buttons  of  aluminium  which  I  have  prepared  are  so 
malleable  that  they  may  be  beaten  and  rolled  out  into  the 
finest  foil  without  cracking  on  the  edges.  They  have  a  strong 
metallic  lustre.  Some  small  pieces,  not  globular,  however, 
were  found  in  the  bottom  of  the  crucible,  and  occasionally  ad- 
hering to  it,  which  cracked  on  being  hammered,  and  were  dif- 
ferent in  color  and  lustre  from  the  others.  They  were  evi- 
dently not  so  pure  as  the  greater  number  of  globules,  and  con- 
tained iron.  On  sawing  through  a  large  button  weighing  3.8 
grammes,  it  could  readily  be  observed  that  the  metal  for  abotit 
half  a  line  from  the  exterior  was  brittle,  while  in  the  interior  it 
was  soft  and  malleable.  Sometimes  the  interior  of  a  globule 
contained  cavities.  With  Deville,  I  have  occasionally  observed 
aluminium  crystallized.  A  large  button  became  striated  and 
crystalline  on  cooling.  Deville  believes  he  has  observed  reg- 
ular octahedra,  but  does  not  state  this  positively.  According 
to  my  brother's  examination,  the  crystals  do  not  belong  to  any 
of  the  regular  forms.    As  I  chanced  on  one  occasion  to  attempt 


the  fusion  of  a  large,  flattened- out  button  of  rather  impure 
aluminium,  without  a  flux,  I  observed,  before  the  heat  was  suffi- 
cient to  fuse  the  mass,  small  globules  sweating  out  from  the 
surface.  The  impure  metal  being  less  fusible  than  pure  metal, 
the  latter  expands  in  fusing  and  comes  to  the  surface." 

Experiments  of  Percy  and  Dick  (1855). 

After  the  publication  of  Rose's  results,  widespread  attention 
was  directed  toward  this  field,  and  it  was  discovered  that  some 
six  months  previously  Dr.  Percy,  in  England,  had  accomplished 
almost  similar  results,  and  had  even  shown  a  specimen  of  the 
metal  to  the  Royal  Institution,  but  with  the  singular  fact  of  ex- 
citing very  little  attention.  These  facts  are  stated  at  length  in 
the  following  paper  written  by  Allan  Dick,  Esq.,  which  ap- 
peared in  November,  1855,  two  months  after  the  publication  of 
H.  Rose's  paper: — * 

"  In  the  last  number  of  this  magazine  was  the  translation  of  a 
paper  by  H.  Rose,  of  Berlin,  describing  a  method  of  preparing 
aluminium  from  cryolite.  Previously,  at  the  suggestion  of  Dr. 
Percy,  I  had  made  some  experiments  on  the  same  subject  in 
the  metallurgical  laboratory  of  the  School  of  Mines ;  and  as  the 
results  obtained  agree  very  closely  with  those  of  Mr.  Rose,  it 
may  be  interesting  to  give  a  short  account  of  them  now,  though 
no  detailed  description  was  published  at  the  time,  a  small  piece 
of  metal  prepared  from  cryolite  having  simply  been  shown  at 
the  weekly  meeting  of  the  Royal  Institution,  March  30,  1855, 
accompanied  by  a  few  words  of  explanation  by  Faraday. 

"  Shortly  after  the  publication  of  Mr.  Deville's  process  for 
preparing  aluminium  from  aluminium  chloride,  I  tried  along 
with  Mr.  Smith  to  make  a  specimen  of  the  metal,  but  we  found 
it  much  more  difficult  to  do  than  Deville's  paper  had  led  us  to 
anticipate,  and  had  to  remain  contented  with  a  much  smaller 
piece  of  metal  than  we  had  hoped  to  obtain.  It  is,  however, 
undoubtedly  only  a  matter  of  time,  skill,  and  expense  to  join 

*  Phil.  Mag.,  Nov.  1855. 


successful  practice  with  the  details  given  by  Deville.  Whilst 
making  these  experiments,  Dr.  Percy  had  often  requested  us  to 
try  whether  cryolite  could  be  used  instead  of  the  chlorides,  but 
some  time  elapsed  before  we  could  obtain  a  specimen  of  the 
mineral.  The  first  experiments  were  made  in  glass  tubes 
sealed  at  one  end,  into  which  alternate  layers  of  finely  powdered 
cryolite  and  sodium  cut  into  small  pieces  were  introduced,  and 
covered  in  some  instances  with  a  layer  of  cryolite,  in  others  by 
sodium  chloride.  The  tube  was  then  heated  over  a  gas  blow- 
pipe for  a  few  minutes  till  decomposition  had  taken  place,  and 
the  product  was  melted.  When  cold,  on  breaking  the  tube,  it 
was  found  that  the  mass  was  full  of  small  globules  of  aluminium, 
but  owing  to  the  specific  gravity  of  the  metal  and  flux  being 
nearly  alike,  the  globules  had  not  collected  into  a  button 
at  the  bottom.  To  effect  this,  long-continued  heat  would  be 
required,  which  cannot  be  given  in  glass  tubes  owing  to  the 
powerful  action  of  the  melted  fluoride  on  them.  To  obviate 
this  difficulty,  a  platinum  crucible  was  lined  with  magnesia 
by  ramming  it  in  hard  and  subsequently  cutting  out  all  but 
a  lining.  In  this,  alternate  layers  of  cryolite  and  sodium  were 
placed,  with  a  thickish  layer  of  cryolite  on  top.  The  cruci- 
ble was  covered  with  a  tight-fitting  lid,  and  heated  to  redness 
for  about  half  an  hour  over  a  gas  blowpipe.  When  cold  it  was 
placed  in  water,  and  after  soaking  for  some  time  the  contents 
were  dug  out,  gently  crushed  in  a  mortar,  and  washed  by  de- 
cantation.  Two  or  three  globules  of  aluminium,  tolerably  large 
considering  the  size  of  the  experiment,  were  obtained,  along 
with  a  large  number  of  very  small  ones.  The  larger  ones  were 
melted  together  under  potassium  chloride.  Some  experiments 
made  in  iron  crucibles  were  not  attended  with  the  same  success 
as  those  of  Rose :  no  globules  of  any  considerable  size  re- 
mained in  the  melted  fluorides ;  the  metal  seemed  to  alloy  on 
the  sides  of  the  crucible,  which  acquired  a  color  like  zinc.  It 
is  possible  that  this  difference  may  have  arisen  from  using  a 
higher  temperature  than  Rose,  as  we  made  these  experiments 
in  a  furnace,  not  over  the  blowpipe.     Porcelain  and  clay  cru- 


cibles  were  also  tried,  but  laid  aside  after  a  few  experiments, 
owing  to  the  action  of  the  fluorides  upon  them,  which  in  most 
cases  was  sufificient  to  perforate  them  completely." 

Deville's  Methods  (1856-8). 

*  "  I  have  repeated  and  confirmed  all  the  experiments  of  Dr. 
Percy  and  H.  Rose,  using  the  specimens  of  cryolite  which  I 
obtained  from  London  through  the  kindness  of  MM.  Rose  and 
Hofmann.  I  have,  furthermore,  reduced  cryolite  mixed  with 
sodium  chloride  by  the  battery,  and  I  believe  that  this  will  be 
an  excellent  method  of  covering  with  aluminium  all  the  other 
metals,  copper  in  particular.  Anyhow,  its  fusibility  is  consid- 
erably increased  by  mixing  it  with  aluminium-sodium  chloride. 
Cryolite  is  a  double  fluoride  of  aluminium  and  sodium,  con- 
taining 13  per  cent,  of  aluminium  and  having  the  formula 
AlFj.sNaF.  I  have  verified  these  facts  myself  by  many 

"  In  reducing  the  cryolite  I  placed  the  finely  pulverized  mix- 
ture of  cryolite  and  sodium  chloride  in  alternate  layers  with 
sodium  in  a  porcelain  crucible.  The  uppermost  layer  is  of 
pure  cryolite,  covered  with  salt.  The  mixture  is  heated  just  to 
complete  fusion,  and  after  stirring  with  a  pipe-stem,  is  let  cool. 
On  breaking  the  crucible,  the  aluminium  is  often  found  united 
in  large  globules,  easy  to  separate  from  the  mass.  The  metal 
always  contains  silicon,  which  increases  the  depth  of  its  natural 
blue  tint  and  hinders  the  whitening  of  metal  by  nitric  acid,  be- 
cause of  the  insolubility  of  the  silicon  in  that  acid.  M.  Rose's 
metal  is  very  ferruginous.  I  have  verified  all  M.  Rose's  ob- 
servations, and  I  agree  with  him  concerning  the  return  of 
metal,  which  I  have  always  found  very  small.  There  are  al- 
ways produced  in  these  operations  brilliant  flames,  which  are 
observed  in  the  scoria  floating  on  the  aluminium,  and  which 
are  due  to  the  gas  burning  and  exhaling  a  very  marked  odor 
of  phosphorus.     In  fact,  phosphoric  acid  exists  in  cryolite,  as 

*  Ann.  de  Chim.  et  de  Phys.  [3],  xlvi.  451. 


one  may  find  by  treating  a  solution  of  the  mineral  in  sulphuric 
acid  with  molybdate  of  ammonia,  according  to  H.  Rose's  re- 

"  M.  Rose  has  recommended  iron  vessels  for  this  operation, 
because  of  the  rapidity  with  which  alkaline  fluorides  attack 
earthen  crucibles  and  so  introduce  considerable  silicon  into  the 
metal.  Unfortunately,  these  iron  crucibles  introduce  iron  into 
the  metal.  This  is  an  evil  inherent  in  this  method,  at  least  in 
the  present  state  of  the  industry.  The  inconveniences  of  this 
method  result  in  part  from  the  high  temperature  required  to 
complete  the  operation,  and  from  the  crucible  being  in  direct 
contact  with  the  fire,  by  which  its  sides  are  heated  hotter  than 
the  metal  in  the  crucible.  The  metal  itself,  placed  in  the  lower 
part  of  the  fire,  is  hotter  than  the  slag.  This,  according  to  my 
observations,  is  an  essentially  injurious  condition.  The  slag 
ought  to  be  cool,  the  metal  still  less  heated,  and  the  sides  of 
the  vessel  where  the  fusion  occurs  ought  to  be  as  cold  as  pos- 
sible. The  yield  from  cryolite,  according  to  Rose's  and  my  own 
observations,  is  also  very  small.  M.  Rose  obtained  from  lo  of 
cryolite  and  4  of  sodium  about  0.5  of  aluminium.  This  is  due 
to  the  affinity  of  fluorine  for  aluminium,  which  must  be  very 
strong  not  only  with  relation  to  its  affinity  for  sodium,  but  even 
for  calcium,  and  this  affinity  appears  to  increase  with  the  tem- 
perature, as  was  found  in  my  laboratory.  Cryolite  is  most 
convenient  to  employ  as  a  flux  to  add  to  the  mixture  which  is 
fused,  especially  when  operating  on  a  small  scale. 

"The  argument  which  decided  the  company  at  Nanterre  not 
to  adopt  the  method  of  manufacture  exclusively  from  cryolite 
was  the  report  of  M.  de  Chancourtois,  mining  engineer,  who 
had  just  returned  from  a  voyage  to  Greenland.  According  to 
the  verbal  statements  of  this  gentleman,  the  gite  at  Evigtok  is 
accessible  only  during  a  very  short  interval  of  time  each  year, 
and,  because  of  the  ice  fields,  can  only  be  reached  then  by  a 
steamboat.  The  workmen  sent  from  Europe  to  blast  and  load 
up  the  rock  have  scarcely  one  or  two  months  of  work  possible. 
The  local  workmen  remain  almost  a  whole  year  deprived  of  all 


communication  with  the  rest  of  the  world,  without  fresh  provi- 
sions or  fuel  other  than  that  brought  from  Europe  in  the  short 
interval  that  navigation  is  open.  The  deposit  itself,  which  is 
scarcely  above  sea-level,  can  be  easily  worked  with  open  roof, 
but  the  neighborhood  of  the  sea  in  direct  contact  with  the  vein, 
the  unorganized  manner  of  working,  and  the  lack  of  care  in 
keeping  separate  the  metalliferous  portions  of  the  ore — all  com- 
bine to  render  the  mineral  very  costly,  and  further  developments 
underground  almost  impossible. 

"  It  is  therefore  fortunate  that  cryolite  is  not  indispensable, 
for  no  one  would  wish  to  establish  an  industry  based  on  the 
employment  of  a  material  which  is  of  such  uncertain  supply." 

Tissier  Bros.'  Method  (1857). 

The  process  adopted  in  the  works  at  Amfreville,  near  Rouen, 
directed  by  Tissier  Bros.,  is  essentially  that  described  by  Percy 
and  Rose.  The  method  of  operating  is  given  by  the  Tissier 
Bros,  themselves  in  their  book  as  follows : 

"After  having  finely  powdered  the  cryolite,  it  is  mixed  with 
a  certain  quantity  of  sodium  chloride  (sea  salt),  then  placed  be- 
tweeen  layers  of  sodium  used  in  the  proportions  given  by  M. 
Rose,  in  large  refractory  crucibles.  These  are  heated  either  in 
a  reverberatory  furnace  or  in  a  wind  furnace  capable  of  giving 
a  temperature  high  enough  to  melt  the  fluoride  of  sodium  pro- 
duced by  the  reaction.  As  the  sodium  fluoride  requires  a 
pretty  high  temperature  to  fuse  it,  the  heat  will  necessarily  be 
higher  than  that  required  in  the  reduction  of  the  double 
chloride  of  aluminium  and  sodium.  When  the  contents  of  the 
crucible  are  melted,  so  as  to  be  quite  liquid,  the  fusion  is  poured 
into  cast-iron  pots,  at  the  bottom  of  which  the  aluminium  col- 
lects in  one  or  several  lumps." 

Tissier  Bros,  claimed  the  following  advantages  for  the  use  of 
cryolite : 

"  Cryolite  comes  to  us  of  a  purity  difficult  to  obtain  with  the 
double  chloride  of  aluminium  and  sodium,  to  which  it  exactly 
corresponds ;   and  since,  thanks  to  the  perfection  we  have  at- 


tained  in  using  it,  the  return  of  aluminium  is  exactly  correspon- 
dent to  the  amount  of  sodium  used  in  reduction,  it  is  easily  seen 
what  immense  advantages  result  from  its  employment.  The 
double  chloride  deteriorates  in  the  air,  it  gives  rise  in  the  works 
to  vapors  more  or  less  deleterious  and  corrosive,  and  its  price 
is  always  high.  Cryolite  can  be  imported  into  France  at  a 
price  so  low  that  we  have  utilized  it  economically  for  making 
commercial  carbonate  of  soda ;  it  remains  unaltered  in  the  air, 
emits  no  deleterious  vapors,  and  its  management  is  much  more 
easy  than  that  of  the  double  chloride.  Moreover,  on  compar- 
ing the  residues  of  the  two  methods  of  reduction,  the  manufac- 
ture from  double  chloride  leaves  sodium  chloride,  almost  with- 
out value,  while  the  manufacture  from  cryolite  leaves  sodium 
fluoride,  which  may  be  converted  for  almost  nothing  into 
caustic  soda  or  carbonate,  and  so  completely  cancels  the  cost 
of  the  cryolite  from  the  cost  of  aluminium.  The  most  serious 
objection  which  can  be  made  to  using  cryolite  is  that  the 
sources  of  the  mineral  being  up  to  the  present  very  limited,  the 
future  prospect  of  aluminium  Hes  necessarily  in  the  utilization 
of  clays  and  their  transformation  into  aluminium  chloride ;  but, 
admitting  that  other  sources  of  cryolite  may  not  be  discov- 
ered hereafter,  the  abundance  of  those  which  exist  in  Greenland 
will  for  a  long  time  to  come  give  this  mineral  the  preference  in 
the  manufacture  of  aluminium." 

The  most  serious  difhculty  which  this  process  had  to  meet, 
and  which  it  could  not  overcome,  was  the  high  content  of  sili- 
con in  the  metal  produced.  A  specimen  of  their  aluminium 
made  in  1859  contained  4.4  per  cent,  of  silicon  alone  (see  p. 
54,  Analysis  7).  The  firm  at  Rouen  went  out  of  business  about 
1863  or  1865 — I  am  unable  to  give  the  exact  date.  From  that 
time  until  quite  recently,  it  has  been  considered  that  the  best 
use  of  cryolite  is  as  a  flux  in  the  preparation  of  aluminium  from 
aluminium-sodium  chloride,  in  which  case  the  slag  is  not  sodium 
fluoride,  but  aluminium  fluoride,  which  acts  but  slightly  on  the 
containing  vessel. 


Wohler' s  Modifications  (1856). 

Wohler  suggested  the  following  modifications  of  Deville's 
process  of  reducing  cryolite  in  crucibles,  by  means  of  which 
the  reduction  can  be  performed  in  an  earthen  crucible  without 
the  metal  produced  taking  up  silicon. 

*"The  finely  pulverized  cryolite  is  mixed  with  an  equal 
weight  of  a  flux  containing  7  parts  sodium  chloride  to  9  parts 
potassium  chloride.  This  mixture  is  then  placed  in  alternate 
layers  with  sodium  in  the  crucible,  50  parts  of  the  mixture  to 
10  of  sodium,  and  heated  gradually  just  to  its  fusing  point. 
The  metal  thus  obtained  is  free  from  silicon,  but  only  one-third 
of  the  aluminium  in  the  cryolite  is  obtained."  In  spite  of  the 
small  yield,  this  method  was  used  for  some  time  by  Tissier 

Gerhard's  Furnace  (1858). 

This  furnace  was  devised  for  the  reduction  of  aluminium 
either  from  aluminium-sodium  chloride  or  from  cryolite,  the 
object  being  to  prevent  loss  of  sodium  by  ignition.  It  was  in- 
vented and  patented  by  W.  F.  Gerhard. |  "  It  consists  of  a 
reverberatory  furnace  having  two  hearths,  or  of  two  crucibles, 
or  of  two  reverberatory  furnaces,  placed  one  above  the  other 
and  communicating  by  an  iron  pipe.  In  the  lower  is  placed  a 
mixture  of  sodium  with  the  aluminium  compound,  and  in  the 
upper  a  stratum  of  sodium  chloride,  or  of  a  mixture  of  this 
salt  and  cryolite,  or  of  the  slag  obtained  in  a  previous  ope- 
ration. This  charge,  when  melted,  is  made  to  run  into  the 
lower  furnace  in  quantity  sufficient  to  completely  cover  the 
mixture  contained  therein,  and  so  to  protect  it  from  the  air. 
The  mixture  thus  covered  is  reduced  as  by  the  usual  operation." 

Whether  a  furnace  was  ever  put  up  and  operated  on  this 
principle,  the  author  cannot  say.  It  is  possible  that  it  may 
have  been  used  in  the  English  manufactory  started  in  1859 
at  Battersea  near  London.     (See  p.  18.) 

*  Ann.  der  Chem.  und  Pharm.  99,255. 
t  Eng.  Pat.,  1858,  No.  2247. 


Thompson  and  White's  Patent  (1887). 

*  J.  B.  Thompson  and  W.  White  recommend  heating  a  mix- 
ture of  3  parts  sodium  and  4  parts  cryolite  to  100°,  whereby 
the  sodium  becomes  pasty  and  the  whole  can  be  well  kneaded 
together  with  an  iron  spatula.  When  cold,  4  parts  of  alumin- 
ium chloride  are  added,  and  the  mixture  put  into  a  hopper  on 
top  of  a  well-heated  reverberatory  furnace,  with  a  cup-shaped 
hearth.  The  charge  is  dropped  into  the  furnace  and  the 
reaction  takes  place  at  once.  To  produce  alloys,  this  patent 
claims  16  parts  of  cryolite  are  mixed  with  5  parts  of  sodium, 
the  metal  added  before  reduction  and  the  mixture  treated  as 
above,  by  which  means  explosions  are  avoided.  The  pre- 
liminary heating  to  100°  is  effected  in  a  jacketed  cast-iron  pot 
connected  with  a  circulating  boiler. 

Hampe's  Experiment  (1888). 

t  Dr.  W.  Hampe  failed  to  produce  aluminium  bronze  by  treat- 
ing cryolite  with  sodium  in  the  presence  of  copper.  A  mixture  of 

Finely  divided  copper 44  grammes, 

Sodium,  in  small  pieces, 15         " 

Finely  powdered  cryolite 100        " 

was  melted  rapidly  in  a  carbon-lined  crucible.  There  were  no 
sounds  given  out  such  as  usually  accompany  other  reductions 
by  sodium,  but  much  sodium  vapor  was  given  off.  The  copper 
button  contained  only  traces  of  aluminium. 

Netto's  Process  (1887). 

Dr.  Curt  Netto,  of  Dresden,  patented  in  England  and  Ger- 
many, in  spring  and  autumn  of  1887,  processes  for  producing 
sodium  and  potassium  and  methods  of  using  them  in  producing 
aluminium.  His  experiments  were  made  in  conjunction  with 
Dr.  Salomon,  of  Essen,  and  the  fact  that  the  experimental  ap- 

*  English  patent  8427,  June  11,  1887. 
tChemiker  Zeitung,  (Cothen),  xii,  p.  391. 


paratus  was  put  up  in  Krupp's  large  steel  works  at  Essen  gave 
rise  to  reports  that  the  latter  had  taken  up  the  manufacture  of 
aluminium  by  some  new  and  very  successful  process,  intending 
to  use  it  for  alloys  in  making  cannon.  * 

In  the  latter  part  of  1888  was  formed  the  Alliance  Aluminium 
Co.  of  London,  England,  capitalized  at  ;£'5oo,ooo,  purposing  to 
manufacture  sodium  and  aluminium,  and  owning  the  English, 
French,  German,  and  Belgian  patents  of  Dr.  Netto  for  the  pro- 
duction of  those  metals,  also  the  processes  of  a  Mr.  Cunning- 
ham for  the  same  purpose,  also  a  process  for  the  production  of 
artificial  cryolite  by  the  regeneration  of  slag  (provisionally  pro- 
tected by  its  inventor,  Mr.  Forster,  of  the  Lonesome  Chemical 
Works,  Streatham),  and,  lastly,  a  process  invented  by  Drs. 
Netto  and  Salomon  by  which  aluminium  can  be  raised  to  the 
highest  standards  of  purity  on  a  commercial  scale.  A  note 
accompanying  the  above  announcement  stated  that  the  exhaust- 
ive experiments  made  at  Essen  had  satisfactorily  demonstrated 
the  practicability  of  the  processes,  and  that  the  company  had 
already  contracted  with  the  cryolite  mines  of  Greenland  for  all 
the  cryolite  they  would  need. 

In  June,  i888,t  the  Alliance  Aluminium  Company  had  in 
operation  a  small  aluminium  plant  at  King's  Head  Yard,  Lon- 
don, E.  C,  and  when  the  process  was  in  continuous  opera- 
tion the  cost  of  the  metal  was  set  down  at  6  shillings  per 
pound.  It  is  probable  that  the  metal  exhibited  in  the  Paris 
Exposition  of  1889  was  produced  at  this  place. 

In  April,  1889,!  ten  acres  of  ground  had  been  leased  at 
Hepburn  on  which  to  produce  sodium  by  Capt.  Cunningham's 
process.  The  sodium  produced  was  to  be  sent  to  Wallsend  to 
be  used  by  the  Alliance  Aluminium  Company,  who  were  erect- 
ing a  large  works  at  that  place. 

As  for  Capt.  Cunningham's  sodium  processes,  they  are  ap- 
parently identical  with  Dr.  Netto's.     Cunningham's  aluminium 

♦American  Register,  Paris,  August,  1888. 
t  Engineering,  June  i,  1888. 
X  E.  and  M.  J.,  April  27,  1889. 



process*  consists  in  melting  the  sodium  to  be  used  with  lead, 
in  order  to  facihtate  the  submerging  of  the  sodium  under  the 
molten  aluminium  salt.  The  alloy  is  cast  into  bars  and  added 
piece  by  piece  to  the  bath  of  molten  aluminium  salt  on  the 
hearth  of  a  reverberatory  furnace.  After  the  reaction  the  mix- 
ture separates  by  specific  gravity  into  lead,  containing  a  little 
aluminium,  and  aluminium  containing  a  little  lead,  the  slag 
floating  on  top  of  all.  Aluminium  is  known  to  have  so  small  an 
attraction  for  lead  that  this  result  becomes  possible. 

Fig.  26. 

Dr.  Netto  recommends  several  processes,  the  one  used  at 
London  being  the  following: — | 

One  hundred  parts  of  cryolite  and  30  to  100  parts  of  sintered 
sodium  chloride  are  melted  at  a  red  heat  in  a  well-covered  clay 
crucible.  (Another  arrangement,  and  apparently  a  better,  is  to 
melt  this  mixture  on  the  hearth  of  a  reverberatory  furnace  and 
tap  it  into  a  deep,  conical  ladle,  in  which  the  succeeding  opera- 
tions proceed  as  about  to  be  described.  See  Fig.  26.)  As  soon 
as  the  bath  is  well  fused,  35  parts  of  sodium  at  the  end  of  a  rod,  and 

*  English  Patent,  16727,  Dec.  5,  1887. 

t  German  Patent  (D.  R.  P.),  45198,  March  26,  1887. 


covered  over  by  a  perforated  concave  plate  is  pushed  quickly 
down  to  the  bottom  of  the  crucible.  The  plate  mentioned  fits 
across  the  whole  section  of  the  crucible  at  its  lower  part,  so  that 
the  fusible,  easily  volatile  sodium,  being  vaporized,  is  divided  into 
very  fine  streams  as  it  passes  upwards  through  the  bath,  and  is 
all  utilized  before  it  reaches  the  surface.  In  this  way  the  re- 
action is  almost  instantaneous,  and  the  contents  can  be  poured 
out  at  once  into  iron  pots,  where,  on  cooling,  the  metal  is  found 
as  a  large  lump  at  the  bottom. 

It  is  further  observed  that  to  avoid  explosions  on  introducing 
the  sodium  it  should  have  in  it  no  cavities  which  might  contain 
moisture  or  hydrocarbons.  In  consequence  of  the  reaction  be- 
ing over  so  quickly,  and  the  heat  set  free  in  the  reduction,  the 
syrupy  fusion  becomes  thin  as  water,  and  the  aluminium  dis- 
seminated through  the  mass  collects  together  completely,  so 
that  the  slag  contains  no  particles  visible  to  the  eye.  Since  the 
reduction,  pouring,  and  cooling  take  place  so  quickly,  the  alu- 
minium is  not  noticeably  redissolved  by  the  bath,  thus  insuring 
a  high  return  of  metal.  By  using  35  parts  of  sodium  to  100 
parts  of  cryolite,  10  parts  of  aluminium  are  obtained.  Since 
the  cryolite  contains  13  per  cent,  of  aluminium,  the  return  is 
yy  per  cent,  of  the  amount  of  metal  in  the  cryolite;  since  35 
parts  of  sodium  should  theoretically  displace  14  parts  of  alu- 
minium, the  return  is  71  per  cent,  of  the  amount  which  the 
sodium  should  produce.  Dr.  Netto  claims  that  this  is  double 
the  return  formerly  obtained  from  cryolite.  The  metal  pro- 
duced is  said  to  be  from  98.5  to  99  per  cent.  pure. 

The  apparatus  erected  at  Krupp's  works  at  Essen,  which  was 
described  by  the  newspapers  as  similar  to  a  Bessemer  converter, 
was  constructed  and  operated  as  follows :  A  large  iron  cylinder 
is  pivoted  at  the  centre  in  a  manner  similar  to  a  Bessemer  con- 
verter. Passing  through  the  centre  of  the  cylinder,  longitudi- 
nally, is  a  large  iron  tube  in  which  generator  gas  is  burnt  to 
heat  the  vessel..  To  heat  it  up,  it  is  placed  erect,  connection 
made  with  the  gas-main,  while  a  hood  above  connects  with  the 
chimney.     On  top  of  the  cylinder,  a  close  valve  communicates 


with  the  interior,  for  charging,  and  at  the  other  end  is  a  tap- 
hole.  The  charge  of  cryoHte  being  put  in,  the  flame  is  passed 
through  the  central  tube  until  the  mineral  is  well  fused.  Then 
soHd  or  melted  sodium  is  passed  in  at  the  top,  the  valve  is 
screwed  tight,  the  gas  shut  off,  and  the  whole  cylinder  is  rotated 
several  times  until  reduction  is  complete,  when  it  is  brought 
upright,  the  tap-hole  opened  and  slag  and  metal  tapped  into  a 
deep  iron  pot,  where  they  separate  and  cool.  Aluminium  thus 
made  could  not  but  contain  much  iron,  even  up  to  14  per  cent., 
it  is  said,  which  would  prevent  its  use  for  any  purpose  ex- 
cept alloying  with  iron.  To  procure  pure  aluminium,  the  ves- 
sel would  have  to  be  properly  fettled. 

Dr.  Netto  also  devised  an  arrangement  similar  to  Heaton's 
apparatus  for  making  steel.  It  consisted  of  a  large,  well-lined 
vessel  on  trunnions,  the  bottom  of  which  was  filled  to  a  certain 
depth  with  sodium,  then  a  perforated  aluminium  plate  placed 
like  a  false  bottom  over  it.  On  pouring  molten  cryolite  into 
the  vessel,  the  aluminium  plate  prevented  the  sodium  from  rising 
en  masse  to  the  surface  of  the  cryolite.  After  the  reaction  was 
over,  the  vessel  was  tilted  and  the  slag  and  metal  poured  out 
into  iron  pots. 

The  modification  of  the  crucible  method  appears  to  have 
been  the  most  feasible  of  Netto's  processes,  and  was  probably 
that  used  at  Wallsend  by  the  Alliance  Aluminium  Com- 
pany. Outside  estimates  of  the  cost  of  aluminium  to  this  com- 
pany placed  it  at  $1.50  to  $2  per  pound.  They  were  selling  in 
the  latter  part  of  1889  at  11,  13,  and  15  shillings  per  pound, 
according  to  quality,  but  were  forced  out  of  the  business  by  the 
electrolytic  processes  in  189 1. 

Grabau's  Process  (1887). 

There  is  only  one  patentee  claiming  particularly  the  reduc- 
tion of  aluminium  fluoride  by  sodium — Ludwig  Grabau,  of 
Hannover,  Germany.  His  patents  on  this  subject  are  im- 
mediately preceded  by  others  on  a  method  of  producing  the 
aluminium  fluoride  cheaply,  which  are  described  on  p.  171,  and 


the  inventor  has  patented  a  process  which  will  furnish  him  with 
cheap  sodium.  Mr.  Alexander  Siemens  is  authority  for  the 
statement  that  a  plant  was  in  operation  in  the  spring  of  1889, 
in  Hannover,  producing  aluminium  by  this  process  on  a  com- 
mercial scale.  The  principal  object  of  Mr.  Grabau's  endeavors 
has  been  to  produce  metal  of  a  very  high  degree  of  purity.  To 
this  end  every  precaution  is  taken  to  procure  pure  materials 
and  to  prevent  contamination  during  reduction.  We  will  quote 
from  a  paper  written  by  Mr.  Grabau*  and  also  from  his  speci- 
fications,f  the  following  explanation  of  the  process : 

"  The  purifying  of  impure  aluminium  is  accompanied  by  so 
many  difficulties  that  it  appears  almost  impossible.  It  is  there- 
fore of  the  greatest  importance  to  so  conduct  the  operation  that 
every  impurity  is  excluded  from  the  start.  Molten  aluminium 
compounds,  whether  a  flux  is  added  or  not,  attack  any  kind  of 
refractory  vessels  and  become  siliceous  if  these  vessels  are  made 
of  chamotte  or  like  materials,  or  if  made  of  iron  they  become 
ferruginous.  These  impurities  are  reduced  in  the  further  pro- 
cesses and  pass  immediately  into  the  aluminium  as  iron,  silicon, 
etc.  Evidently  the  case  is  altered  if  an  aluminium  compound 
which  is  infusible  can  be  used  advantageously.  Aluminium 
fluoride  is  infusible  and  also  retains  its  pulverized  condition 
when  heated  up  to  the  temperature  needed  for  its  use ;  it  can 
therefore  be  heated  in  a  vessel  of  any  kind  of  refractory  mater- 
ial, or  even  in  a  metallic  retort,  without  danger  of  taking  up  any 

"  Further,  it  is  necessary  for  succeeding  in  producing  alu- 
minium that  the  reduced  metal  thall  unite  to  a  large  body  after 
the  reduction.  For  this  purpose  all  previous  processes  use 
fluxes,  and  usually  cryolite.  But  cryolite  is  impure,  and  there- 
fore here  is  a  source  of  many  of  the  impurities  in  commercial 
aluminium.  Dr.  K.  Kraut,  of  Hannover,  has  observed  that, 
according  to  the  recent  analyses  of  Fresenius  and  Hintz,  com- 

*  Zeitschrift  fur  angewandte,  Chemie,  1889,  vol.  6. 

t  German  Pat.  (D.  R.  P.)  47°3'.  Nov.  15,  1887.     English  Pat.  15593,  Nov.  14, 
1887.     U.  S.  Patents  386704,  July  24,  l888;  and  400449,  April  2,  1889. 


mercial  cryolite  contains  0.80  to  1.39  per  cent,  of  silicon,  and 
o.ii  to  0.88  per  cent,  of  iron,  and  that  these  impurities  inter- 
penetrate the  mineral  in  such  a  manner  as  to  be  often  only  vis- 
ible under  the  microscope,  and  therefore  totally  impossible  of 
removal  by  mechanical  means.  It  is  thus  seen  that  the  avoid- 
ance of  the  use  of  any  Rux  is  of  great  importance  as  far  as 
producing  pure  metal  is  concerned,  as  well  as  from  an  eco- 
nomic standpoint. 

"  By  the  following  process  it  is  also  possible  to  reduce  alu- 
minium fluoride  by  ?odium  without  the  vessel  in  which  reduc- 
tion takes  place  being  attacked  either  by  the  aluminium-sodium 
fluoride  formed  or  by  the  reduced  aluminium.  For  this  pur- 
pose the  aluminium  fluoride  and  sodium  are  brought  together 
in  such  proportions  that  after  the  reaction  there  is  still  suffi- 
cient aluminium  fluoride  present  to  form  with  the  sodium  flu- 
oride resulting  from  the  reaction  a  compound  having  the  com- 
position of  cryolite.     The  reaction,  therefore,  will  be 


"  Using  these  proportions,  the  aluminium  fluoride  must  be 
previously  warmed  up  to  about  600°  C,  in  order  that  when  it  is 
showered  down  upon  the  melted  sodium  the  reaction  may  com- 
mence without  further  application  of  heat.  The  aluminium 
fluoride  remains  granular  at  this  temperature  and  therefore  re- 
mains on  top  of  the  melted  sodium,  like  saw-dust  or  meal  upon 
water,  and  under  its  protection  the  reaction  proceeds  from 
below  upwards — an  important  advantage  over  the  usual  method 
of  pouring  molten  aluminium  compounds  on  to  sodium,  in 
which  the  lighter  sodium  floats  to  the  top  and  burns  to  waste. 
If  solid  sodium  is  used  in  my  process  the  aluminium  fluoride 
must  be  somewhat  hotter  on  being  poured  into  the  reduction 
vessel,  or  about  700°  C.  For  carrying  out  the  process  the  re- 
duction vessel  must  be  artificially  cooled,  so  as  to  form  a  lining 
by  chilling  some  of  the  aluminium-sodium  fluoride  formed  by 
the  reaction,  on  the  inner  walls.  This  lining  is  in  no  wise 
further  attacked  by  the  contents  of  the  vessel,  nor  can  it  evi- 
dently supply  to  them  any  impurity. 



Fig.  27. 


"The  furnace  A  (Fig.  27)  with  grate  B  and  chimney  C, 
serves  for  heating  the  iron  retorts  D  and  E,  which  are  coated 
with  chamotte  and  protected  from  the  direct  action  of  the  flame 
by  brick  work.  The  vessel  D  serves  for  heating  the  aluminium 
fluoride,  and  is  provided  with  a  damper  or  sliding  valve  be- 
neath. The  sodium  is  melted  in  E,  and  can  be  emptied  out  by 
turning  the  cock  k.  The  water-jacketed  reduction  vessel  is 
mounted  on  trunnions  to  facilitate  emptying  it.  The  retorts 
are  first  heated  dark  red-hot,  and  D  is  filled  with  the  conven- 
ient quantity  of  aluminium  fluoride.  When  this  has  become 
red  hot,  as  is  shown  by  a  small  quantity  of  white  vapor  is- 
suing from  it,  the  required  quantity  of  sodium  is  put  into  E. 
This  melts  very  quickly,  and  is  then  immediately  run  into  the 
reduction  vessel  by  opening  the  stop-cock  k.  As  soon  as  it  is 
transferred,  the  slide  at  the  base  of  the  retort  D  is  pulled  out 
and  the  whole  quantitity  of  aluminium  fluoride  falls  at  once 
upon  the  sodium,  and  the  reaction  begins.  As  before  re- 
marked, the  granular  form  of  the  aluminium  fluoride  keeps  it 
on  top  of  the  sodium,  so  that  the  latter  is  completely  covered 
during  the  whole  reaction.  This  prevents  almost  altogether 
any  waste  of  sodium  by  volatilization.  Dr.  K.  Kraut  testifies 
to  an  operation  which  he  witnessed  in  which  the  return  showed 
83  per  cent,  of  the  sodium  to  have  been  utilized.  An  efficiency 
in  this  respect  of  over  90  per  cent,  has  been  occasionally 
reached,  while  the  average  is  80  to  90.  Ad.  Wurtz  states  that 
the  average  for  several  years'  working  of  the  Deville  process 
showed  only  74.3  per  cent,  of  the  quantity  of  aluminium  pro- 
duced which  the  sodium  used  could  have  given. 

"During  the  reaction  a  very  high  temperature  is  developed, 
so  that  the  cryolite  formed  becomes  very  fluid,  but  is  chilled 
against  the  sides  of  the  vessel  to  a  thickness  of  a  centimetre  or 
more.  This  crust  is  a  poor  conductor  of  heat,  and  is  neither 
attacked  by  the  fluid  cryolite  nor  by  the  aluminium.  In  con- 
sequence of  the  great  fluidity  of  the  bath,  it  is  possible  for  the 
aluminium  to  unite  into  a  body  without  the  use  of  any  flux, 
The  reaction  being  over,  which  is  accomplished  with  the  above 


proportions  of  materials  in  a  few  seconds,  and  the  vessel  hav- 
ing been  shaken  briskly  backwards  and  forwards  a  few  times  to 
facilitate  the  settling  of  the  aluminium,  the  whole  is  turned  on 
the  trunnions  and  emptied  into  a  water-jacketed  iron  pot,  where 
it  cools.  The  crust  of  cryolite  inside  the  reduction  vessel  is 
left  there,  and  the  apparatus  is  ready  for  another  operation." 

M.  Grabau,  in  a  private  communication  to  the  author,  sums 
up  the  advantages  of  his  process,  including  the  production  of 
the  aluminium  fluoride,  as  follows : — 

1.  The  process  is  not  dependent  on  natural  cryolite, which  is 
expensive,  impure  and  not  easily  purified. 

2.  The  raw  material — aluminium  sulphate — can  be  procured 
in  large  quantities  and  of  perfect  purity. 

3.  The  aluminium  fluoride  is  produced  by  a  wet  process, 
which  offers  no  difficulties  to  production  on  a  large  scale. 

4.  The  fluorspar  may  be  completely  freed  from  foreign 
metals  by  washing  with  dilute  acid ;  any  silica  present  is  not 
injurious,  as  it  remains  undissolved  in  the  residue  during  the 

5.  The  cryolite  formed  in  each  reduction  contains  no  impur- 
ities, and  an  excess  of  it  is  produced  which  can  be  sold. 

6.  The  reduction  of  aluminium  fluoride  by  my  method  gives 
a  utilization  of  80  to  90  per  cent,  of  the  sodium  used,  which  is 
much  more  than  can  be  obtained  by  other  processes. 

7.  Aluminium  fluoride  is  infusible,  and  can  therefore  be 
heated  in  a  vessel  of  any  refractory  material  without  taking  up 
any  impurities.  It  is  also  unchanged  in  the  air,  and  can  be 
kept  unsealed  for  any  length  of  time  without  deteriorating  in 
the  least. 

8.  No  flux  has  to  be  added  for  reduction,  the  use  of  impure 
flux  being  a  frequent  cause  of  impurity  of  the  metal. 

In  point  of  fact,  M.  Grabau  has  succeeded  in  producing  sev- 
eral hundred  pounds  of  aluminium  averaging  over  99^  per 
cent.  pure.  Dr.  Kraut  reports  an  analysis  of  an  average  speci- 
men with  99.62  per  cent,  of  aluminium  (see  Analysis  20,  p.  54), 
and  metal  has  been  made  as  pure  as  99.8  per  cent.,  a  piece  of 


which  has  been  kindly  forwarded  the  author  by  M.  Grabau,  and 
I  freely  admit  it  to  be  as  fine  a  specimen  of  aluminium  as  I  have 
ever  seen.  Metal  of  such  purity  and  fineness  can  only  be  made 
by  the  electrolytic  processes  at  considerable  expense  over  ordi- 
nary best  commercial  metal,  since  they  must  use  chemically  pure 
alumina  and  extra  precautions  as  to  the  purity  of  the  electrodes. 
It  therefore  appears  possible  that  M.  Grabau  may  yet  be  able 
to  manufacture  and  sell  this  extra  quality  aluminium,  if  he  can 
bring  its  price  anywhere  near  that  of  the  electrolytic  aluminium. 
The  Grabau  Aluminium  Werke,  Trotha,  Germany,  operates  the 
Grabau  processes,  and  does  a  business  in  manufacturing  and 
selling  sodium. 



As  preliminary  to  the  presentation  of  the  various  electrolytic 
methods  which  have  been  proposed  or ,  used,  it  may  be  profit- 
able to  review  briefly  the  principles  of  electro-metallurgy  as 
they  apply  to  the  decomposition  of  aluminium  compounds. 
Some  additional  observations  have  been  already  included  in 
Chapter  VIII. 

The  atomic  weight  of  aluminium  being  27,  its  chemical 
equivalent,  or  the  weight  of  it  equal  in  consbining  power  to  one 
part  of  hydrogen,  is  9.  Therefore  a  current  of  quantity  sufiS- 
cient  to  liberate  i  part  of  hydrogen  in  a  certain  time  would 
produce  9  parts  of  aluminium  in  the  same  time,  according  to 
the  fundamental  law  of  electric  decomposition.  It  has  been 
determined  that  a  current  of  i  ampere  acting  for  one  second, 
liberates  0.00001035  grammes  of  hydrogen;  therefore  it  will 
produce  or  set  free  from  combination  in  the  same  time, 
0.00009315  grammes  of  aluminium.  This  is  the  electro-chemical 
equivalent  of  aluminium.  Now,  from  thermo-chemical  data  we 
know  that  the  amount  of  energy  required  to  set  free  a  certain 
weight  of  aluminium  will  vary  with  the  compound  from  which 
it  is  produced ;  but  the  above  equivalent  is  independent  of  the 
compound  decomposed,  therefore  there  must  be  some  varying 
factor  connected  with  the  quantity  of  the  current  to  account 
for  the  different  amounts  of  work  which  the  current  does  in 
decomposing  diflferent  compounds  of  the  same  element.  This 
is  exactly  in  accordance  with  the  principles  of  the  mechanical 
or  thermal  equivalent  of  the  electric  current,  for  the  statement 
"  a  current  of  one  ampere,"  while  it  expresses  a  definite  quan- 



tity  of  electricity,  yet  carries  no  idea  of  the  energy  represented 
by  that  current;  we  must  know  against  what  resistance  or  with 
what  electro- motive  force  that  quantity  is  moved,  and  then  we 
can  calculate  its  mechanical  equivalent.  Now,  a  current  of  i 
ampere  flowing  against  a  resistance  of  i  ohm,  or  in  other 
words,  with  a  moving  force  or  intensity  of  i  volt,  represents  a 
quantity  of  energy  in  one  second  equal  to  0.00024  calories  of 
heat  or  to  O.I  kilogrammetre  of  work,  and  is  therefore  nearly 
^ijf  of  a  horse  power.  Therefore  we  can  calculate  the  theoreti- 
cal intensity  of  current  necessary  to  overcome  the  affinities  of 
any  aluminium  compound  for  which  we  know  the  appropriate 
thermal  data.  For  instance,  when  aluminium  forms  its  chlo- 
ride (see  p.  228)  ^ — — — =5,960   calories    are    developed    per 

kilo  of  aluminium  combining ;  consequently  the  liberating  of 
0.00009315  grammes  of  aluminium  (its  electro-chemical  equiva- 
lent), requires  the  expenditure  of  an  amount  of  energy  equal  to 
0.00009315  X  5.960  =  0.000555  calories.  Since  a  current  of 
I  ampere  at  an  intensity  of  i  volt  represents  only  0.00024  cal- 
ories, the  intensity  of  current  necessary  to  decompose  alumin- 
ium chloride  is  theoretically — '- — ^=  2.3  volts.     In  a  simi- 


lar  manner  we  can  calculate  that  to  decompose  alumina  would 

,     .  ^.       ,  ,  391600       0.00000009315 

require  an  electro-motive  force  of x Z^-^  = 

54  0.00024 

2.8   volts.     These   data   would    apply   only  to    the  substances 

named,  in  a  fused  anhydrous  state ;   with  hydrated  aluminium 

chloride  in  solution,  a  far. greater  electro-motive  force  would  be 

necessary.     If  we  had  the  thermal  data  we  could  also  calculate 

the  intensity  of  current  necessary  to  decompose  the  sulphate, 

nitrate,  acetate,  etc.,  in  aqueous  solution;    but  failing  these,  we 

can  reason  from  analogy  that  it  would  be  several  volts  in  each 


It  must  be  noted  also,  that  these  heats  of  combination  are 

those  observed  at  ordinary  temperatures.     To  find  the  voltage 

required  at  high  temperatures  we  must  make  allowance  for  the 


weakening  of  the  affinities,  that  is,  for  the  decrease  in  heat  of 
combination  as  the  temperature  rises.  When  the  rate  of  this 
decrease  is  known,  the  true  voltage  required  at  any  temperature 
can  be  calculated.  Often  the  operation  is  reversed ;  that  is,  the 
minimum  electro-motive  force  required  to  effect  decomposition 
is  accurately  measured  at  different  temperatures,  and  from 
these  data  the  variation  in  the  heat  of  formation  with  the  tem- 
perature can  be  calculated  by  reversing  the  above  calculations. 
For  example  of  this  see  p.  239. 

To  utilize  such  calculations,  we  must  bear  in  mind  exactly 
what  they  represent.  To  decompose  fused  aluminium  chloride, 
for  instance,  not  only  must  the  current  possess  an  intensity  of 
2.3  volts,  but  it  must  in  addition  have  power  enough  above  this 
to  overcome  the  transfer  resistance  of  the  electrolyte ;  i.  e.,  to 
force  the  current  through  the  bath  from  one  pole  to  the  other. 
So,  then,  2.3  volts  would  be  the  absolute  minimum  of  intensity 
which  would  produce  decomposition,  and  the  actual  intensity 
practically  required  would  be  greater  than  this,  varying  with 
the  distance  of  the  poles  apart  and  the  temperature  of  the 
bath  as  far  as  it  affects  the  conducting  power  of  the  electrolyte. 
From  this  it  would  immediately  follow  that  if  the  substance  to 
be  decomposed  is  an  absolute  non-conductor  of  electricity,  no 
intensity  of  current  will  be  able  to  decompose  it.  If,  on  the 
other  hand,  the  substance  is  a  conductor  and  the  poles  are 
within  reasonable  distance,  a  current  of  a  certain  intensity  will 
always  produce  decomposition.  The  objection  is  immediately 
made  that  in  most  cases  no  metal  is  obtained  at  all,  which  is 
true  not  because  none  is  produced,  but  because  it  is  often  dis- 
solved by  secondary  actions  as  quickly  as  it  is  produced.  I 
need  but  refer  to  the  historic  explanation  of  the  decomposition 
of  caustic  soda  in  aqueous  solution,  although  we  have  cases 
hardly  parallel  to  this  in  which  the  electrolyte  itself  dissolves 
the  separated  metal. 

How  about  the  case  of  aqueous  solutions  ?  Water  requires  a 
minimum  electro-motive  force  of  1.5  volts  to  decompose  it, 
and  hence  a  prominent  electrician  remarked  of  a  compound 


which  theoretically  required  over  2  volts  that  its  decomposition 
in  aqueous  solution  would  involve  the  decomposition  of  the 
water  and  therefore  was  impossible.  This  remark  is  only  partly 
true ;  for  caustic  soda  requres  over  2  volts,  yet  if  mercury  is 
present  to  absorb  the  sodium  as  it  is  set  free  and  protect  it  from 
the  water,  we  will  obtain  sodium,  while  the  water  is  decomposed 
at  the  same  time.  The  truth  seems  to  be  that  if  two  substances 
are  present  which  require  different  electro-motive  forces  to  de- 
compose them,  a  current  of  a  certain  intensity  will  decompose 
the  one  requiring  the  least  force,  without  affecting  the  other  at 
all;  but,  if  it  is  of  an  intensity  sufficient  to  decompose  the 
higher  compound,  then  the  current  will  be  divided  in  some  ratio 
between  the  two,  decomposing  them  both.  This  theory  would 
render  theoretically  possible  the  decomposition  of  aluminium 
salts  in  aqueous  solution,  with  a  waste  of  power  proportional  to 
the  amount  of  water  decomposed  at  the  same  time ;  but 
whether  any  aluminium  would  be  obtained  would  be  contingent 
on  the  secondary  action  of  the  water  on  the  aluminium.  Pure 
aluminium  in  mass  is  not  acted  upon  by  water,  but  the  foil  is 
rapidly  eaten  away  by  boihng  water.  The  state  of  division  of 
the  metal,  then,  determines  the  action  of  water  on  it,  and  it  is 
altogether  probable  that  the  reason  why  aluminium  is  not  easily 
deposited  from  aqueous  solution  is  that,  like  sodium,  it  is 
attacked  as  soon  as  isolated,  the  acidity  of  the  solution  convert- 
ing the  hydrate  formed  back  into  the  salt,  or  else  simply  the 
hydrate  remaining.  Unfortunately,  mercury  does  not  exercise 
the  same  function  with  aluminium  as  with  sodium,  for  water  at- 
tacks its  amalgam  with  aluminium,  and  so  destroys  the  metal. 
It  is  possible  that  if  some  analogous  solvent  could  be  found  which 
protected  the  aluminium  from  the  action  of  water,  the  deposi- 
tion from  aqueous  solution  could  be  performed  quite  easily. 

The  electro-deposition  of  a  metal  using  a  soluble  anode  is 
entirely  a  different  affair.  In  this  case,  while  the  salt  in  solu- 
tion is  decomposed,  yet  it  is  immediately  regenerated  by  the 
acid  radical  set  free  dissolving  from  the  anode  just  the  same 
quantity  of  metal  as  was  deposited  at  the  cathode.     This  action 


exactly  counterbalances  the  electromotive  force  required  for 
decomposition,  and  leaves  only  the  conduction  resistance  of  the 
bath  to  be  overcome.  If  this  resistance  is  kept  down  so  that 
the  tension  required  to  operate  the  bath  is  less  than  or  not 
much  greater  than  1.5  volts,  and  the  bath  is  well  supplied  with 
salt,  there  will  be  no  water  decomposed  and  a  good  plating 
may  be  obtained.  This  has  been  already  practised  on  a  large 
scale  with  aluminium. 

With  anodes,  however,  which  do  not  dissolve,  the  decom- 
position of  the  salt  necessarily  involves  that  of  the  water,  if  over 
1.5  volts  are  required  to  decompose  it.  The  result  of  this  is 
that  hydrogen  gas  is  set  free  liberally  at  the  cathode  along  with 
the  metal,  and  prevents  the  latter  from  depositing  as  a  smooth, 
dense  metal,  causing,  in  fact,  the  production  of  "sponge." 
This  finely-divided  spongy  metal  is  in  the  very  best  condition 
to  decompose  water,  and  the  result  is  its  oxidation.  However, 
the  metal  can  only  decompose  water  at  a  certain  rate ;  the  oxi- 
dation does  not  take  place  instantaneously.  If  then  we  de- 
posit the  metal  faster  than  it  can  waste  away  by  oxidation,  by 
using  a  current  of  large  quantity,  we  may  succeed  in  gaining 
metal  and  thus  secure  a  deposit.  This  way  of  overcoming  the 
difficulty  is  assisted  by  using  a  very  strong  solution,  which  al- 
lows a  current  of  large  quantity  to  pass  with  less  resistance, 
and  also  leaves  less  water  uncombined  to  act  on  the  metal. 
By  using  these  devices,  Bunsen  was  enabled  to  obtain  even 
metallic  calcium  from  a  solution  of  its  chloride. 

By  the  density  of  the  current  we  mean  the  number  of  am- 
peres passing  through  each  unit  of  surface  of  cathode  or  de- 
positing surface.  If  the  density  is  very  great,  it  is  necessary 
that  a  brisk  circulation  be  kept  up  in  the  solution  to  bring  fresh 
quantities  of  salt  into  the  sphere  of  action  and  to  remove  the 
impoverished  solution ;  otherwise,  if  a  deficiency  of  salt  occurs, 
the  solvent  is  attacked.  Rapid  circulation  therefore  favors 
regular  working. 

In  any  electrolytic  bath,  the  tension  and  density  of  the  cur- 
rent determine  which  of  the  several  ingredients  present  will  be 


decomposed.  Let  us  assume  two  compounds  present,  A  and  B, 
of  which  ^  is  a  weaker  compound  than  By  either  one  of  them 
may  be  water,  or  they  may  both  be  anhydrous  salts.  In  such 
a  liquid  bath,  a  current  just  strong  enough  to  decompose  A 
will  not  afifect  B.  When  the  current  is  just  strong  enough  to 
decompose  B,  the  product  will  be  the  elements  of  A  with  a 
trace  of  those  of  B/  but  since  the  base  in  B  is  supposed  to  be  a 
stronger  one  than  that  in  A,  there  will  be  a  secondary  action, 
and  the  base  of  B  will  displace  the  base  of  A  in  the  still  unde- 
composed  compound,  and  B  will  be  re-formed.  This  will  be 
the  direct  effect  of  increasing  the  tension  of  the  current.  How- 
ever, if  the  density  of  the  current  is  increased  at  the  same  time, 
another  principle  comes  into  play.  The  base  of  B  may  be  de- 
posited so  quickly  that  it  has  not  time  to  react  on  A,  and  in 
that  case  the  deposit  will  contain  the  base  of  B.  Also,  if  there 
is  a  much  larger  proportion  of  B  than  of  A  present,  a  larger 
proportion  of  its  base  will  be  deposited  than  before  and  escape 
re-solution.  Also,  other  things  being  equal,  if  the  compound 
B  is  more  fluid  or  rather  diffuses  quicker  in  the  bath  than  A, 
more  of  it  will  get  to  the  electrodes  and  a  larger  proportion  be 

We  therefore  see  that  when  two  or  more  compounds  are 
present,  the  relative  amounts  of  each  to  be  decomposed  depend 

1.  Primarily,   on  the    electro-motive    force    of   the    current, 
which  may  be  so  regulated  as  to  decompose  them  one  after  the  " 
other  in  the  order  of  their  electromotive  force  of  decomposition. 

2.  On  the  density  of  the  current  at  the  electrodes.  That  is, 
provided  the  tension  of  the  current  is  sufficient  to  decompose 
the  stronger  compound,  the  greater  the  density  of  the  current 
the  greater  the  proportion  of  the  stronger  compound  which 
will  be  decomposed,  other  conditions  being  equal. 

3.  On  the  relative  amounts  of  each  present.  Other  condi- 
tions being  equal,  the  relative  amount  of  a  compound  decom- 
posed will  increase  as  its  proportion  in  the  bath  is  increased. 

4.  On  the  relative  rates  of  diffusion,  or  the  rapidity  with 
which  elements  of  the  different  compounds  move  towards  the 


The  consideration  of  the  electrolytic  processes  falls  naturally 
under  two  heads : — 

I.  Deposition  from  aqueous  solution. 
II.  Non-aqueous  electric  processes. 


Deposition  of  Aluminium  from  Aqueovs  Solution. 

The  status  of  this  question  is  one  of  the  curiosities  of  electro- 
metallurgic  science.  Evidently  attracted  by  the  great  reward 
to  be  earned  by  success,  many  experimenters  have  labored  in 
this  field,  have  recommended  all  sorts  of  processes,  and  pat- 
ented all  kinds  of  methods.  We  have  inventors  afiSrming  in 
the  strongest  manner  the  successful  working  of  their  methods, 
while  other  experimenters  have  followed  these  recipes,  and 
tried  almost  every  conceivable  arrangement,  yet  report  negative 
results.  To  show  that  it  is  quite  possible  that  many  strong  af- 
firmations may  be  made  in  good  faith,  I  have  only  to  mention 
the  fact  that  in  March,  1863,  Mr.  George  Gore  described  in  the 
Philosophical  Magazine  some  experiments  by  which  he  de- 
posited coatings  of  aluminium  from  aqueous  solutions,  and 
afterwards,  in  his  text  book  of  Electro-metallurgy,  asserts  that 
he  knows  of  no  successful  method  of  doing  this  thing.  We 
infer  that  Mr.  Gore  found  that  he  was  in  error  the  first  time. 
So,  if  we  take  the  position  that  aluminium  cannot  by  any 
methods  so  far  advanced  be  deposited  from  aqueous  solution 
without  using  a  soluble  aluminium  anode,  we  will  have  to  ad- 
mit that  the  proposers  of  many  of  the  following  processes  are 
probably  misled  by  their  enthusiasm  in  affirming  so  strongly 
that  they  can  do  this  thing.  Yet  the  problem  is  not  impossible 
of  solution. 

Messrs.  Thomas  and  Tilly*  coat  metals  with  aluminium  and 
its  alloys  by  using  a  galvanic  current  and  a  solution  of  freshly 
precipitated  alumina  dissolved  in  boihng  water  containing  po- 
tassium   cyanide,    or  a  solution   of   freshly  calcined  alum    in 

*  English  Patent,  1855,  No.  2756. 


aqueous  potassium  cyanide;  also  from  several  other  liquids. 
Their  patent  covers  the  deposition  of  the  alloys  of  aluminium 
with  silver,  tin,  copper,  iron,  silver  and  copper,  silver,  and  tin, 
etc.  etc.,  the  positive  electrode  being  of  this  metal  or  alloy. 

M.  Corbelli,  of  Florence,*  deposits  aluminium  by  electroylz- 
ing  a  mixture  of  rock  alum  or  sulphate  of  alumina  (2  parts) 
with  calcium  chloride  or  sodium  chloride  (i  part)  in  aqueous 
solution  (7  parts),  the  anode  being  mercury  placed  at  the 
bottom  of  the  solution  and  connected  to  the  battery  by  an  iron 
wire  coated  with  insulating  material  and  dipping  its  uncovered 
end  into  the  mercury.  The  zinc  cathode  is  immersed  in  the 
solution.  Aluminium  is  deposited  on  the  zinc,  as  a  blackish 
powder  or  as  a  thin,  compact  sheet,  and  the  chlorine  which  is 
liberated  at  the  anode  unites  with  the  mercury,  forming  calomel. 

J.  B.  Thompsonf  reports  that  he  has  for  over  two  years  been 
depositing  aluminium  on  iron,  steel,  and  other  metals,  and 
driving  it  into  their  surfaces  at  a  heat  of  500°  F.,  and  also  de- 
positing aluminium  bronze  of  various  tints,  but  declines  to  state 
his  process. 

George  Gore,  Jthe  noted  electrician,  recommended  the  fol- 
lowing procedure  for  depositing  aluminium  on  copper,  brass,  or 
German  silver:  — 

"  Take  equal  measures  of  sulphuric  acid  and  water,  or  one 
part  sulphuric  acid,  one  part  hydrochloric  acid  and  two  parts 
of  water,  put  into  it  half  an  ounce  of  pipe  clay  to  the  pint  of 
dilute  acid,  and  boil  for  an  hour.  Take  the  clear,  hot  liquid 
and  immerse  in  it  an  earthen  porous  cell  containing  sulphuric 
acid  diluted  with  ten  times  its  bulk  of  water,  together  with  a 
rod  or  plate  of  amalgamated  zinc.  Connect  the  zinc  with  the 
positive  wire  of  a  Smee  battery  of  three  or  four  elements  con- 
nected for  intensity.  The  article  to  be  coated,  well  cleaned,  is 
connected  with  the  negative  pole  and  immersed  in  the  hot  clay 
solution.     In  a  few  minutes  a  fine,  white  deposit  of  aluminium 

*  English  Patent,  1858,  No.  507. 
fChem.  News,  xxiv.  194  (1871). 
t  Philosophical  Magazine,  March,  1863. 


will  appear  all  over  its  surface.  It  may  then  be  taken  out, 
washed  quickly  in  clean  water,  wiped  dry,  and  polished.  If  a 
thicker  coating  is  required,  it  must  be  taken  out  as  soon  as  the 
deposit  becomes  dull,  washed,  dried,  polished,  and  re-immersed, 
and  this  must  be  repeated  at  intervals  as  often  as  it  becomes 
dull,  until  the  required  thickness  is  obtained.  It  is  necessary 
to  have  the  acid  well  saturated  by  boiling,  or  no  deposit  will 
be  obtained." 

Mierzinski  asserts  that  Dr.  Gore  was  mistaken  when  he  sup- 
posed this  deposit  to  be  aluminium,  and  in  Gore's  Text  Book 
of  Electro-metallurgy  no  mention  is  made  of  these  experi- 
ments, the  author  thereby  acknowledging  the  error.  As  to 
what  the  deposit  could  have  been,  we  are  left  to  conjecture, 
since  no  explanation  has  been  advanced  by  Dr.  Gore ;  it  may 
possibly  have  been  silicon,  mercury,  or  zinc,  as  all  three  of 
these  were  present  besides  aluminium. 

J.  A.  Jeanfon*  has  patented  a  process  for  depositing  alumin- 
ium from  an  aqueous  solution  of  a  double  salt  of  aluminium 
and  potassium  of  specific  gravity  1.161  ;  or  from  any  solution 
of  an  aluminium  salt,  such  as  sulphate,  nitrate,  cyanide,  etc., 
concentrated  to  20°  B.  at  50°  F.  He  uses  a  battery  of  four 
pairs  of  Smee's  or  three  Bunsen's  cells,  with  elements  arranged 
for  intensity,  and  electrolyzes  the  solutions  at  140°  F.  The 
first  solution  will  decompose  without  an  aluminium  anode,  but 
the  others  require  such  an  anode  on  the  negative  pole.  The 
solution  must  be  acidulated  slightly  with  acid  corresponding  to 
the  salt  used,  the  temperature  being  kept  at  140°  F.  constantly. 

More  recently!,  Jeangon  has  obtained  a  patent  for  the  fol- 
lowing process :  "  Subjecting  a  supersaturated  acid  solution  of 
a  salt  of  aluminium  to  the  action  of  a  current  passed  from  an 
anode  of  aluminium  in  a  state  of  division  or  porosity,  pre- 
senting a  relatively  large  exposure  of  surface  within  a  given 
field  of  electric  force,  and  a  suitable  metallic  cathode."    Further 

*  Annual  Record  of  Science  and  Industry,  1875. 

tU.  S.  Patent,  436,895;  Sept.  23,  i8go.     (Specimens.) 


details  state  that  the  anode  is  to  be  prepared  by  melting  alu- 
minium iri  a  crucible  and  stirring  in  about  30  per  cent,  of  car- 
bon or  a  similar  substance,  and  then  moulding  into  shape.  The 
electrolyte  is  to  be  maintained  at  a  high  temperature,  preferably 
180°  to  200°  F.,  under  which  conditions  a  dense  deposit  is 

The  writer  has  already  stated  that  aluminium  is  being  suc- 
cessfully electro-plated  from  solution  using  aluminium  anodes; 
and,  if  the  above  process  is  the  one  which  has  been  used  in 
Philadelphia  by  the  Harvey  Filley  Plating  Co.,  then  I  can  cer- 
tify to  it  having  been  successfully  operated.  The  company 
mentioned  refuse  to  say  anything  about  the  process  they  use, 
but  I  have  been  informed  by  outside  parties  that  the  above  is 
the  one.  It  is  certain,  however,  that  very  good  specimens  of 
aluminium-plated  ware  have  been  made  and  sold  by  this  firm, 
several  having  been  examined  and  tested  by  the  writer  person- 
ally. A  thin  deposit  on  sheet-iron,  which  has  been  in  my  pos- 
session over  two  years,  shows  no  sign  of  rust  or  deterioration, 
and  suggests  the  practicability  of  thus  making  a  substitute  for 
tin-plate  of  greater  durability  and  which  will  not  rust. 

M.  A.  Bertrand  *  states  that  he  deposited  aluminium  on  a 
plate  of  copper  from  a  solution  of  double  chloride  of  aluminium 
and  ammonia,  by  using  a  strong  current,  and  the  deposit  was 
capable  of  receiving  a  brilliant  polish. 

Jas.  S.  Haurd,t  of  Springfield,  Mass.,  patented  the  elec- 
trolysis of  an  aqueous  solution  formed  by  dissolving  cryolite  in 
a  solution  of  magnesium  and  manganous  chlorides. 

John  Braun  {  decomposes  a  solution  of  alum,  of  specific 
gravity  1.03  to  1.07,  at  the  usual  temperature,  using  an  insolu- 
ble anode.  In  the  course  of  the  operation,  the  sulphuric  acid 
set  free  is  neutralized  by  the  continual  addition  of  alkali ;  and, 
afterwards,  to  avoid  the  precipitation  of  alumina,  a  non-volatile 
organic  acid,  such  as  tartaric,  is  added  to  the  solution.     The 

*  Chem.  News,  xxiv.  227. 

t  U.  S.  Patent,  228,900,  June  15,  1880. 

X  German  Patent,  No.  28,760  (1883'!. 


intensity  of  the  current  is  to  be  so  regulated  that  for  a  bath  of 
lO  to  20  Htres  two  Bunsen  elements  (about  20  centimetres 
high)  are  used. 

Dr.  Fred.  Fischer*  stated  that  Braun's  proposition  was  con- 
trary to  his  experience.  By  passing  a  current  of  8  to  9  volts 
and  50  amperes,  using  from  o.i  to  10  amperes  per  sq.  centi- 
metre of  cathode,  with  various  neutral  and  basic  aluminium 
sulphate  solutions,  with  and  without  organic  acids,  he  obtained 
no  aluminium.  He  obtained  a  black  deposit  of  copper  sul- 
phide on  the  copper  anode,  which  had  apparently  been  mis- 
taken by  Braun  for  aluminium. 

Moses  G.  Farmer  |  has  patented  an  apparatus  for  obtaining 
aluminium  electrically,  consisting  of  a  series  of  conducting  cells 
in  the  form  of  ladles,  each  ladle  having  a  handle  of  conducting 
material  extending  upwards  above  the  bowl  of  the  next  suc- 
ceeding ladle ;  each  ladle  can  be  heated  separately  from  the 
rest ;  the  anodes  are  hung  in  the  ladles,  being  suspended  from 
the  handles  of  the  preceding  ladles,  the  ladles  themselves  being 
the  cathodes. 

M.  L.  Senet  X  electrolyzes  a  saturated  solution  of  aluminium 
sulphate,  separated  by  a  porous  septum  from  a  solution  of 
sodium  chloride.  A  current  is  used  of  6  to  7  volts  and  4 
amperes.  The  double  chloride,  AlCl'.NaCl,  is  formed,  then 
decomposed,  and  the  aluminium  liberated  deposited  on  the 
negative  electrode.  It  has  later  been  remarked  of  this  process 
that  it  has  not  had  the  wished-for  success  on  a  large  scale. 

Col.  Frismuth,  of  Philadelphia,  purported  to  plate  an  alloy  of 
nickel  and  aluminium.  He  used  an  ammoniacal  solution,  prob- 
ably of  their  sulphates.  The  plating  certainly  resembled 
nickel,  but  that  it  contained  aluminium  the  writer  is  not  pre- 
pared to  assert. 

Baron    Overbeck    and    H.   Neiwerth,  of    Hannover,  §    have 

*  Zeitschrift  des  Vereins  Deutsche  Ingenieurs,  1884,  p.  557. 
t  U.  S.  Patent,  No.  315,266,  April,  1885. 
t  Cosmos  les  Mondes,  Aug.  10,  1885. 
§  English  Pat.,  Dec.  15,  1883,  No.  5756: 

3  1 2  ALUMINIUM. 

patented  the  following  process :  An  aqueous  or  other  solu- 
tion of  an  organic  salt  of  aluminium  is  used,  or  a  mixture  of 
solutions  which  by  double  decomposition  will  yield  such  salt. 
Or  a  mixture  of  a  metallic  chloride  and  aluminium  sulphate 
may  be  used,  this  yielding  nascent  aluminium  chloride,  which 
the  current  splits  up  immediately  into  aluminium  and  chlorine. 

Herman  Reinbold*  gives  the  following  recipe,  stating  that  it 
furnishes  excellent  results :  50  parts  of  potash  alum  are  dis- 
solved in  300  parts  of  water,  and  to  this  are  added  10  parts  of 
aluminium  chloride.  The  whole  is  then  heated  to  200°  F., 
cooled,  and  then  39  parts  of  potassium  cyanide  added.  A 
weak  current  should  be  used.  It  is  stated  that  the  plating, 
when  polished,  will  be  found  equal  to  the  best  silver  plating. 
"  Iron,"  noticing  this  process,  remarks,  "  there  are  a  number  of 
formulae  for  electro-plating  with  aluminium,  but  few  appear  to 
have  attained  to  practical  utility  in  the  arts,  for  the  reason  that 
there  is  no  special  demand  for  such  processes.  All  the  quali- 
ties that  are  possessed  by  an  electro-deposit  of  aluminium  are 
possessed  to  an  equal  or  superior  degree  by  other  metals,  silver, 
nickel,  platinum,  etc.  Furthermore,  it  obstinately  refuses  to 
take  and  to  retain  a  high  lustre."  This  criticism  is  a  little 
overdrawn,  since  the  one  quality  in  which  aluminium  is  super- 
ior to  silver — not  blackening  by  contact  with  sulphurous  vapor 
— is  not  mentioned. 

Under  the  name  of  Count  R.  de  Montegelas,  of  Philadelphia, 
several  patents  have  been  taken  out  in  England  for  the  elec- 
trolysis of  aqueous  solutions,  which  may  be  summarized  as 
follows : — 

f  Alumina  is  treated  with  hydrochloric  acid,  and  aluminium 
chloride  obtained  in  solution.  The  liquid  is  then  placed  in  a 
vessel  into  which  dip  a  suitable  anode  and  a  cathode  of  brass  or 
copper.  On  passing  an  electric  current  through  the  bath  the 
iron  present  in  the  liquid  is  first  deposited,  and  as  soon  as  this 
deposition  ceases  (as  is  apparent  by  the  change  of  color  of  the 

*  Jeweler's  Journal,  September,  1887. 

t  English  Patent,  Aug.  18,  1886,  No.  10607. 


deposit)  the  liquid  is  decanted  into  another  similar  bath,  and  to 
it  is  added  about  fifty  per  cent,  by  weight  of  the  oxide  of  either 
lead,  tin  or  zinc.  On  sending  a  current  through  this  bath, 
aluminium  together  with  the  metal  of  the  added  oxide  is  said  to 
be  deposited  on  the  cathode. 

*  A  rectangular  vessel  is  divided  into  two  unequal  compart- 
ments by  a  vertical  porous  partition,  into  the  smaller  of  which 
is  placed  a  saturated  solution  of  common  salt,  in  which  is  im- 
mersed a  brass  or  copper  electrode ;  into  the  larger  is  put  a  so- 
lution of  aluminium  chloride,  immersed  in  which  is  an  alumin- 
ium electrode.  On  passing  the  current  the  latter  solution, 
which  is  normally  yellow,  is  gradually  decolorized  and  con- 
verted into  a  solution  of  aluminium-sodium  chloride.  When 
colorless,  this  solution  is  taken  out  and  the  aluminium  deposited 
in  a  similarly  arranged  vessel.  The  double  chloride  solution  is 
placed  in  the  larger  compartment,  with  an  electrode  of  brass, 
copper,  or  a  thin  plate  of  aluminium,  while  the  smaller  com- 
partment contains  a  carbon  electrode  dipping  into  a  solution  of 
salt  and  surrounded  by  fragments  of  a  mixture  of  salt  and 
double  chloride,  fused  together  in  equal  parts. 

The  author  has  been  given  several  ounces  of  a  very  fine  me- 
tallic powder  said  to  have  been  made  by  these  processes,  and 
which  is  certainly  aluminium.  As  I  am  not  satisfied,  however, 
that  the  specimen  is  really  authentic,  I  feel  justified  in  suspend- 
ing a  final  expression  of  opinion  on  the  process. 

A  Walker,  of  Tarnowitz,  has  patented  the  following  methods 
of  procedure : j 

a.  Pure  commercial  hydrate  is  dissolved  in  nitric  acid  free 
from  chlorine,  in  slight  excess,  and  tartaric  acid  added.  The 
Hquid  is  let  clear  for  some  time,  any  potassium  bi-tartrate, 
which  may  be  formed  from  small  quantities  of  potassium  ad- 
hering to  the  hydrate,  filtered  out,  and  the  clear  solution 
electrolyzed.    There  is  added  to  the  solution  during  electrolysis 

*  English  Patent,  Feb.  3,  1887,  No.  1751. 
t  German  Pat.  (D.  R.  P.)  40,626  (1887). 

3  1 4  ALUMINIUM. 

organic  acid — as  formic,  acetic,  citric,  oxalic — or,  better,  ab- 
solute alcohol. 

b.  A  solution  of  aluminium  nitrate,  as  far  as  possible  free 
from  alkalies  and  sulphuric  acid,  is  decomposed  by  a  strong 
dynamic  current  in  baths  arranged  in  series,  using  platinized 
plates  as  anode  and  cathode.  With  a  weak  current  of  0.02  to 
0.05  amperes  to  a  square  centimetre,  the  aluminium  separates 
out  on  the  cathode  as  a  deep  black  deposit,  sticking  close  to 
the  copper.  The  cathode  is  lifted  from  the  solution,  freed  from 
small  quantities  of  alumina  coating  it  by  gentle  rinsing,  and 
then  the  deposit  washed  off  by  a  strong  jet  of  water.  The 
powder  obtained  is  washed  further  with  clear,  cold  water,  par- 
ticularly free  from  sodium  chloride,  and  dried  by  gentle  heat- 
ing in  the  air. 

H.  C.  Bull*  proposes  to  manufacture  aluminium  alloys  by 
using  the  metal  to  be  alloyed  with  aluminium  as  a  cathode  in  a 
bath  of  aluminium  sulphate,  the  anode  being  either  of  alumin- 
ium or  of  an  insoluble  substance.  When  enough  aluminium  is 
deposited,  the  cathode  is  taken  out  and  melted  down. 

C.  A.  Burghardt  and  W.  J.  Twining,  of  Manchester,  England, 
have  patented  the  following  methods  : 

fTo  a  solution  of  sodium  or  potassium  aluminate  containing 
about  7.2  oz.  of  aluminium  per  gallon  are  added  4  pounds  of 
95  per  cent,  potassium  cyanide  dissolved  in  a  quart  of  water, 
and  then  gradually  2j^  pounds  of  potassium  bi-carbonate. 
The  whole  is  boiled  12  hours  and  made  up  to  a  gallon.  The 
bath  is  used  at  175°  F.  with  aluminium  or  platinum  anode  and 
carbon  or  copper  cathode.  The  addition  of  a  little  free  hydro- 
cyanic acid  insures  a  bright  deposit  when  articles  are  being 

%  Two  and  one-half  kilos  of  aluminium  sulphate  in  solution  is 
precipitated  by  ammonia,  and  then  re-dissolved  by  adding  \yi 
kilos  of  caustic  soda  dissolved  in  a  litre  of  water;   the  alumina 

♦English  Pat.,  10,199  A.  (1887). 

t  English  Pat.,  July  2,  1887,  No.  9389. 

I  German  Pat.  (D.  R.  P.),  45,020  (1887). 


is  thus  slightly  in  excess.  The  hydrocyanic  acid  is  added  until 
a  slight  precipitate  appears.  This  solution,  warmed  to  80°,  is 
used  as  a  bath  from  which  aluminium  is  to  be  deposited. 

*The  bath  is  prepared  by  dissolving  alumina  in  a  solution  of 
chloride  of  copper,  and  treating  further  with  caustic  soda  or 
potash  for  the  purpose  of  causing  the  aluminium  and  copper  to 
combine  together.  The  precipitate,  dissolved  in  hydrocyanic 
acid  and  diluted,  forms  a  bath  of  double  cyanide,  which  when 
electrolyzed  deposits  an  alloy  of  aluminium  and  copper. 

Besides  the  processes  so  far  described,  patents  have  been 
taken  out  in  England  by  Gerhard  and  Smith,f  Taylor,|  and 
Coulson,§  the  details  of  which  have  not  been  accessible  to  the 

Over  against  these  statements  of  enthusiastic  inventors,  let 
me  place  a  few  extracts  from  authorities  who  have  given  much 
time  and  attention  to  the  subject  of  electro-depositing  alumin- 
ium from  solution  without  the  use  of  an  aluminium  anode. 

Sprague||  states  his  inability  to  deposit  aluminium  electric- 
ally from  solution. 

Dr.  Clemens  Winckler  IT  states  that  he  has  spent  much  time 
in  trying  all  methods  so  far  proposed,  and  comes  to  the  conclu- 
sion that  aluminium  cannot  be  deposited  by  electricity  in  the 
wet  way. 

Dr.  Geo.  Gore**  although  having  once  proposed  a  method 
which  he  said  attained  this  end,  yet  in  his  later  work  on  Elec- 
tro-metallurgy does  not  mention  his  former  proposition,  and 
quotes,  apparently  as  coinciding  with  his  own  opinion,  the 
words  of  Sprague  and  Winckler  given  above. 

*  English  Pat.,  Oct.  28,  1887,  No.  2602. 

tNo.  16,653  (1884). 

J  No.  1991  (1855). 

§  No.  207s  (1857). 

II  Sprague's  Electricity,  p.  309. 

t  Journal  of  the  Chem.  Soc,  X.  1 134. 

**  Text-book  of  Electto- metallurgy. 


Dr.  S.  Mierzinski*  states,  in  1883,  that  "the  deposition  of 
aluminium  from  an  aqueous  solution  of  its  salt  has  not  yet  been 

Dr.  W.  Hampef  claims  to  have  shown  that  the  electrolysis 
of  aqueous  aluminous  solutions,  although  frequently  patented, 
is  not  to  be  expected.  From  which  we  would  infer  that  he 
could  not  testify  to  it  ever  having  been  done. 

Alexander  Watt|  holds  that  the  electrolytic  production  of 
aluminium  ,from  solution  is  very  improbable.  He  tried  acid 
solutions,  alkaline  solutions,  cyanide  combinations,  etc.,  under 
most  varied  conditions,  without  any  result. 

Finally,  I  will  quote  from  a  letter  of  my  good  friend  Dr. 
Justin  D.  Lisle,  of  Springfield,  O.,  who  with  ample  means  at 
his  disposal,  an  enthusiasm  bred  of  love  tor  scientific  truth,  and 
talent  to  guide  him  in  his  work,  has  reached  the  following  re- 
sults :  "  I  have  tried  in  almost  every  conceivable  way  to  de- 
posit it  (aluminium)  from  aqueous  solution  by  electricity, 
using  from  i  pint  cells  to  60  gallon  cells  successively ;  the  cells 
were  connected  for  quantity  and  for  intensity;  acid  and  neutral 
solutions  were  used;  carbon,  platinum,  and  copper  electrodes, 
porous  cups  and  diaphragms,  were  all  thoroughly  tried,  without 
the  slightest  deposit  of  metal.  In  some  cases  alumina  was  de- 
posited, which  has  led  me  to  think  that  aluminium  was  pri- 
marily deposited,  and  owing  to  the  fine  state  in  which  it  existed 
was  promptly  oxidized." 

The  following  details  of  the  operation  of  the  electric  plant  of 
the  Tacony  Metal  Company,  near  Philadelphia,  under  the 
supervision  of  Mr.  J.  D.  Darling,  are  all  that  the  writer  has 
been  able  to  gather  respecting  their  process.  This  company 
had  the  contract  to  electroplate  the  exterior  ironwork  of  the 
tower  of  the  Philadelphia  Public  Buildings,  there  being  alto- 
gether about  50,000  square  feet  to  be  plated,  on  which  was  to 
be  deposited  20,000  pounds  of  aluminium,  or  a  little  over  six 

*  Die  Fabrikation  des  Aluminiums. 

tChem.  Zeit.  (Cothen),  XI.  935. 

I  London  Electrical  Review,  July,  1887. 


ounces  to  the  foot.  This  would  give  a  smooth  coating  j\  inch 
thick.  The  cast-iron  work  is  first  given  a  coating  of  copper, 
and  the  aluminium  deposited  on  it,  but  it  is  stated  that  good 
platings  have  been  obtained  directly  on  the  cast-iron. 

The  largest  pieces  plated  were  columns  26  feet  long  and  3 
feet  in  diameter.  The  whole  operation  of  treating  such  a  col- 
umn lasted  1 1  days,  while  the  plant  could  turn  out  one  every 
4  days.     The  operations  were  as  follows  : 

(i)  Boiling  24  hours  in  a  strong  solution  of  caustic  soda, 
after  which  well  washed. 

(2)  Pickled  in  dilute  sulphuric  acid  24  hours,  brushed  vig- 
orously and  washed. 

(3)  Copper-plated  by  immersion  40  hours  in  a  copper 
cyanide(?)  solution.  The  column  was  then  brushed  with  par- 
affine  wax  inside,  any  flaws  soldered  up,  and — 

(4)  Copper-plated  again  in  an  ordinary  copper-plating  so- 
lution for  72  hours,  until  16  ounces  of  copper  to  the  square 
foot  had  been  deposited. 

(5 )  Put  into  the  aluminium-plating  tank,  and  3  ounces  of 
aluminium  per  square  foot  deposited  on  it.  Time,  72  hours. 
Column  then  well  washed  in  the  sixth  tank. 

The  dynamo  used  for  operation  3  gives  a  current  of  1000 
amperes  at  6  volts  tension ;  for  operation  4,  4000  amperes 
at  2.5  volts  tension;  for  operation  5,  2000  amperes  at  8  volts 
tension.  In  the  latter  case,  the  current  density  at  the  depos- 
iting surface  was  8  amperes  per  square  foot  (86  amperes  per 
square  metre).  In  this  depositing  tank,  aluminium  anodes  4 
feet  long,  12  inches  wide  and  }(  inch  thick  were  used.  Sixty 
of  these  plates,  weighing  35  pounds  each,  were  hung  around 
the  inside  of  the  tank. 

■  The  company  will  give  no  information  regarding  the  compo- 
sition of  the  electrolyte.  Concerning  the  conducting  of  thS 
operation,  Mr.  Darling  has  stated  that  "  Aluminium  is  more 
difficult  to  deposit  than  any  of  the  common  metals,  because  of 
its  tendency  to  re-dissolve  after  being  deposited.  I  find  that 
by  using  a  solution  of  aluminium  salt  that  has  but  a  slight  dis- 


solving  effect  on  aluminium,  with  a  density  of  current  of  8 
amperes  per  square  foot,  and  with  sufficiently  high  voltage, 
aluminium  can  be  deposited  at  the  rate  of  i  gramme  per  hour 
per  square  foot  in  a  reguline  state.  With  much  higher  cur- 
rents it  can  be  deposited  quicker,  but  will  be  in  a  pulverulent 
state,  which  does  not  adhere." 


Non-aqueous  Electric  Processes. 

The  above  heading  was  originally  written,  "The  electrolytic 
decomposition  of  fused  aluminium  compounds,"  but  I  have 
changed  it  to  this  form  because  it  is  doubtful,  in  several  cases, 
whether  electrolytic  decomposition  really  plays  much  of  a  role 
in  the  isolation  of  the  aluminium.  In  some  processes  a  pow- 
erful current  is  used  and  largely  converted  into  heat,  producing 
temperatures  never  before  used  in  industrial  operations.  In 
such  cases,  chemical  reactions,  rendered  possible  by  the  very 
high  temperature,  come  into  play  and  may  even  be  the  prin- 
cipal means  of  reducing  the  aluminium  compound.  It  has  been 
suggested  that  such  processes  should  be  classed  apart  as 
"electro-thermal  methods;"  but  such  a  division  does  not  ap- 
pear satisfactory  to  me,  because  in  most  cases  we  cannot  say 
positively  that  electrolysis  does  not  play  some  part,  and  in 
others  it  is  simply  impossible  to  decide  which  of  the  two  agents 
of  reduction,  electrolysis  or  chemical  affinity,  is  the  most  active. 
It  has  been  suggested  also  that  those  processes  in  which  high 
voltage  is  used  cannot  be  electrolytic,  but  must  be  electro-ther- 
mal ;  but  such  a  division  is  not  logical.  If  a  bath  is  taking  a 
high  voltage  to  work  it,  it  may  be  solely  from  poor  conductivity 
in  the  electrolyte,  and  not  because  an  arc  is  formed  in  the  bath, 
and  true  electrolysis  may  be  going  on  to  the  full  extent  of  the 
power  of  the  current.  If  we  knew  definitely,  for  each  process, 
which  action  played  the  principal  part  in  the  reduction,  we 
might  classify  the  processes,  but  such  a  classification  would  not 
be  of  much  use.     If  it  was  absolutely  necessary  to  make  some 


such  division,  I  should  consider  as  electro-thermal  those  pro- 
cesses in  which  the  parts  of  the  apparatus  used  are  not  ar- 
ranged as  they  should  be  to  secure  the  maximum  electrolytic 
decomposition.  We  could  thus,  in  such  cases,  say  at  once, 
from  a  consideration  of  the  apparatus  and  its  manner  of  work- 
ing, that  electrolysis  was  evidently  not  contemplated  in  its  con- 
struction and  could  only  play  a  minor  part  in  its  operation. 

In  conclusion,  I  regard  it  impossible  to  make  an  exact  clas- 
sification of  these  processes  such  as  would  be  of  any  value  to 
the  metallurgist  or  aid  the  general  reader  to  a  better  under- 
standing of  them,  and  I  therefore  take  them  up  in  chronolog- 
ical order. 

Davy's  Experiment  (1810). 

Sir  Humphry  Davy,  in  his  Brompton  Lecture  before  the 
Royal  Philosophical  Society,*  described  the  following  attempt 
to  decompose  alumina  and  obtain  the  metal  of  this  earth.  He 
connected  an  iron  wire  with  the  negative  pole  of  a  battery  con- 
sisting of  1000  double  plates.  The  wire  was  heated  to  white- 
ness and  then  fused  in  contact  with  some  moistened  alumina, 
the  operation  being  performed  in  an  atmosphere  of  hydrogen. 
The  iron  became  brittle,  whiter,  and  on  being  dissolved  in  acid 
gave  a  solution  from  which  was  precipitated  alumina,  identical 
with  that  used. 

It  is  evident  that  the  alumina  had  been  reduced  by  the 
chemical  action  of  the  hydrogen  gas,  a  reaction  which  we  now 
know  takes  place  below  the  fusing  point  of  alumina,  2200°,  and 
probably  begins  as  low  as  1700°. 

Duvivier's  Experiment  (1854). 

M.  Duvivier  f  states  that  by  passing  an  electric  current  from 
eighty  Bunsen  cells  through  a  small  piece  of  laminated  disthene 
between  two  carbon  points,  the  disthene  melted  entirely  in  two 
or  three  minutes ;  the  elements  which  composed  it  were  partly 

*  Philosophical  Transactions,  1810. 
fThe  Chemist,  Aug.,  1854. 


disunited  by  the  power  of  the  electric  current,  and  some  alu- 
minium freed  from  its  oxygen.  Several  globules  of  the  metal 
separated,  one  of  which  was  as  white  and  as  hard  as  silver. 

Since  disthene  is  aluminium  silicate,  formula  Al^Os.SiOj,  it 
is  most  likely  that  the  metal  obtained  was  highly  siliceous 
aluminium,  since  complete  reduction  of  this  compound  would 
give  54  parts  of  aluminium  to  28  parts  of  silicon.  The  highly- 
heated  carbon  particles  of  the  electric  arc  were  most  probably 
the  reducing  agent. 

Bunsen's  and  Deville's  Methods  (1854). 

A  method  of  decomposing  aluminium-sodium  chloride  by  the 
battery  was  discovered  simultaneously  by  Deville  in  France  and 
Bunsen  in  Germany,  in  1854,  and  is  nothing  else  but  an  appli- 
cation of  the  process  already  announced  by  Bunsen  of  decom- 
posing magnesium  chloride  by  the  battery.  Deville  gives  the 
more  minute  account,  and  we  therefore  quote  his  description  of 
the  process. 

f  "  It  appears  to  me  impossible  to  obtain  aluminium  by  the 
battery  in  aqueous  solutions.  I  should  believe  this  to  be  an 
absolute  impossibility  if  the  brilliant  experiments  of  M.  Bunsen 
in  the  preparation  of  barium,  chromium  and  manganese  did  not 
shake  my  convictions.  Still  I  must  say  that  all  the  processes 
of  this  description  which  have  recently  been  published  for  the 
preparation  of  aluminium  have  failed  to  give  me  any  results. 
Every  one  knows  the  elegant  process  by  means  of  which  M. 
Bunsen  has  lately  produced  magnesium,  decomposing  fused  mag- 
nesium chloride  by  an  electric  current.  The  illustrious  profes- 
sor at  Heidelberg  has  opened  up  a  method  which  may  lead  to 
very  interesting  results.  However,  the  battery  cannot  be  used 
for  decomposing  aluminium  chloride  directly,  which  does  not 
melt,  but  volatilizes  at  a  low  temperature ;  it  is,  therefore,  neces- 
sary to  use  some  other  material  which  is  fusible  and  in  which 

*Tbe  Chemist,  Aug.  1854. 

t  Ann.  de  Chem.  et  de  Phys.  [3],  46,  452;  Deville's  "  de  rAluminium." 


aluminium  alone  will  be  displaced  by  the  current.  I  have  found 
this  salt  in  the  double  chloride  of  aluminium  and  sodium,  which 
melts  towards  185°  C,  is  fixed  at  a  somewhat  high  temperature, 
although  volatile  below  the  fusing  point  of  aluminium,  and  thus 
unites  all  the  desirable  conditions. 

"  I  put  some  of  this  double  chloride  into  a  porcelain  crucible 
separated  imperfectly  into  two  compartments  by  a  thin  leaf  of 
porcelain,  and  decomposed  it  by  means  of  a  battery  of  five  ele- 
ments and  carbon  electrodes.  The  crucible  was  heated  more 
and  more  as  the  operation  progressed,  for  the  contents  became 
less  and  less  fusible,  but  the  heat  was  not  carried  past  the  melt- 
ing point  of  aluminium.  Arrived  at  this  point,  after  having 
lifted  out  the  diaphragm  and  electrodes,  I  heated  the  crucible 
to  bright  redness,  and  found  at  the  bottom  a  button  of  alumin- 
ium, which  was  flattened  out  and  shown  to  the  Academy  in  the 
S6ance  of  March  20,  1854.  The  button  was  accompanied  by  a 
considerable  quantity  of  carbon,  which  prevented  the  union  of 
a  considerable  mass  of  shot-metal.  This  carbon  came  from  the 
disintegration  of  the  very  dense  gas-retort  carbon  electrodes;  in 
fact,  the  positive  electrode  was  entirely  eaten  away  in  spite  of 
its  considerable  thickness.  It  was  evident,  then,  that  this  appa- 
ratus, although  similar  to  that  adopted  by  Bunsen  for  manufac- 
turing magnesium,  would  not  suit  here,  and  the  following  is  the 
process  which  after  many  experiments  I  hold  as  best. 

"  To  prepare  the  bath  for  decomposition,  I  heat  a  mixture  of 
2  parts  aluminium  chloride  and  i  part  sodium  chloride,  dry  and 
pulverized,  to  about  200°  in  a  porcelain  capsule.  They  com- 
bine with  disengagement  of  heat,  and  the  resulting  bath  is  very 
fluid.  The  apparatus  which  I  use  for  the  decomposition  com- 
prises a  glazed  porcelain  crucible,  which  as  a  precaution  is 
placed  inside  a  larger  one  of  clay.  The  whole  is  covered  by  a 
porcelain  cover  pierced  by  a  slit  to  give  passage  to  a  large  thick 
leaf  of  platinum,  which  serves  as  the  negative  electrode ;  the  lid 
has  also  a  hole  through  which  is  introduced,  fitting  closely,  a 
well-dried  porous  cylinder,  the  bottom  of  which  is  kept  at  some 
distance  from  the  inside  of  the  porcelain  crucible.     This  porous 



vessel  encloses  a  pencil  of  retort  carbon,  which  serves  as  the 
positive  electrode.  Melted  double  chloride  is  poured  into  the 
porous  jar  and  into  the  crucible  so  as  to  stand  at  the  same 
height  in  both  vessels ;  the  whole  is  heated  just  enough  to  keep 
the  bath  in  fusion,  and  there  is  passed  through  it  the  current 
from  several  Bunsen  cells,  two  cells  being  strictly  sufficient. 
The  annexed  diagram  shows  the  crucibles  in  section. 

Fig.  28. 

"The  aluminium  deposits  with  some  sodium  chloride  on  the 
platinum  leaf;  the  chlorine,  with  a  little  aluminium  chloride,  is 
disengaged  in  the  porous  jar  and  forms  white  fumes,  which  are 
prevented  from  rising  by  throwing  into  the  jar  from  time  to 
time  some  dry,  pulverized  sodium  chloride.  To  collect  the 
aluminium,  the  platinum  leaf  is  removed  when  sufficiently 
charged  with  the  saline  and  metallic  deposit;  after  letting  it 
cool,  the  deposit  is  rubbed  off  and  the  leaf  placed  in  its  former 
position.  The  material  thus  detached,  melted  in  a  porcelain 
crucible,  and  after  cooling  washed  with  water,  yields  a  gray, 
metallic  powder,  which  by  melting  several  times  under  a  layer 
of  the  double  chloride  is  reunited  into  a  button." 

Bunsen*  adopted  a  similar  arrangement.  The  porcelain  cru- 
*  Pogg.  Annalen,  97,  648. 


cible  containing  the  bath  of  aluminium-sodium  chloride  kept  in 
fusion  was  divided  into  two  compartments  in  its  upper  part  by  a 
partition,  in  order  to  separate  the  chlorine  liberated  from  the  alu- 
minium reduced.  He  made  the  two  electrodes  of  retort  carbon. 
To  reunite  the  pulverulent  aluminium,  Bunsen  melted  it  in  a  bath 
of  the  double  chloride,  continually  throwing  in  enough  sodium 
chloride  to  keep  the  temperature  of  the  bath  about  the  fusing 
point  of  silver. 

As  we  have  seen,  Deville,  without  being  acquainted  with  Bun- 
sen's  investigations,  employed  the  same  arrangement,  but  he 
abandoned  it  because  the  retort  carbon  slowly  disintegrated  in 
the  bath,  and  a  considerable  quantity  of  double  chloride  was  lost 
by  the  higher  heat  necessary  to  reunite  the  globules  of  alumin- 
ium after  the  electrolysis.  Deville  also  observed  that  by  working 
at  a  higher  temperature,  as  Bunsen  had  done,  he  obtained  purer 
metal,  but  in  less  quantity.  The  effect  of  the  high  heat  is  that 
silicon  chloride  is  formed  and  volatilizes,  and  the  iron  which 
would  have  been  reduced  with  the  aluminium  is  transformed 
into  ferrous  chloride  by  the  aluminium  chloride,  and  thus  the 
aluminium  is  purified  of  silicon  and  iron. 

Plating  aluminium  on  copper. — The  same  bath  of  double  chlor- 
ide of  aluminium  and  sodium  may  be  used  for  plating  alumin- 
ium in  particular  on  copper,  on  which  Capt.  Caron  experimented 
with  Deville.  Deville  says :  "  To  succeed  well,  it  is  necessary  to 
use  a  bath  of  double  chloride  which  has  been  entirely  purified 
from  foreign  metallic  matter  by  the  action  of  the  battery  itself. 
When  aluminium  is  being  deposited  at  the  negative  pole,  the  first 
portions  of  metal  obtained  are  always  brittle,  the  impurities  in 
the  bath  being  removed  in  the  first  metal  thrown  down;  so, 
when  the  metal  deposited  appears  pure,  the  piece  of  copper  to 
be  plated  is  attached  to  this  pole  and  a  bar  of  pure  aluminium 
to  the  positive  pole.  However,  a  compact  mixture  of  carbon 
and  alumina  can  be  used  instead  of  the  aluminium  anode,  which 
acts  similarly  to  it  and  keeps  the  composition  of  the  bath  con- 
stant. The  temperature  ought  to  be  kept  a  little  lower  than  the 
fusing  point  of   aluminium.     The  deposit  takes  place  readily 


and  is  very  adherent,  but  it  is  difficult  to  prevent  it  being  im- 
pregnated with  double  chloride,  which  attacks  it  the  moment 
the  piece  is  washed.  The  washing  ought  to  be  done  in  a  large 
quantity  of  water  Cryolite  might  equally  as  well  be  used  for 
this  operation,  but  its  fiisibility  should  be  increased  by  mixing 
with  it  a  little  double  chloride  of  aluminium  and  sodium  and 
some  potassium  chloride." 

During  a  recent  law-suit  for  infringement  of  the  Hall  process, 
it  was  held  by  the  defendants  that  Deville  electrolyzed  a  fluoride 
bath,  (cryolite)  in  which  alumina  was  present  and  therefore 
would  be  dissolved.  It  appears  quite  evident,  however,  that 
Deville  did  not  use  cryolite,  because  it  would  have  destroyed 
the  porcelain  crucibles  and  necessitated  the  use  of  special  ap- 
paratus which  Deville  does  not  even  hint  at.  It  is,  moreover, 
true  that  when  alumina  is  mixed  with  carbon  the  latter  prevents 
the  cryoHte  from  wetting  or  coming  into  actual  contact  with  it. 
In  an  experiment  by  the  writer,  a  large  cylinder  of  carbon  into 
which  had  been  incorporated  over  50  per  cent,  of  alumina 
was  kept  in  molten  cryolite  for  several  hours,  and  on  being 
taken  out  showed  not  the  slightest  sign  of  corrosion.  Judges 
Taft  and  Ricks  of  Ohio  very  properly  ruled  that  Deville's  ex- 
periments did  not  in  any  way  disclose  or  operate  on  the  princi- 
ple utilized  by  Mr.  Hall. 

Le  Chatellier's  Method  (1861). 

The  subject  of  this  patent*  was  the  decomposition  of  the 
fused  double  chloride  of  aluminium  and  sodium,  with  the  par- 
ticular object  of  coating  or  plating  other  metals,  the  articles 
being  attached  to  the  negative  pole.  About  the  only  novelty 
claimed  in  this  patent  was  the  use  of  a  mixture  of  alumina  and 
carbon  for  the  anode,  but  we  see  from  the  previous  paragraph 
that  this  was  suggested  by  Deville  several  years  before ;  the 
only  real  improvement  was  the  placing  of  this  anode  inside  a 
porous  cup,  in  order  to  prevent  the  disintegrated  carbon  from 

*  English  Patent,  1861,  No.  1214. 


falling  into  the  bath.     This  was  really  only  the  Deville  process, 
patented  in  England. 

Monckton's  Patent  (1862). 

Monckton*  proposes  to  pass  an  electric  current  through  a 
reduction  chamber,  and  in  this  way  to  raise  the  temperature 
to  such  a  point  that  alumina  will  be  reduced  by  the  carbon 
present.  We  clearly  see  in  this  the  germ  of  several  more- 
recently  patented  processes. 

Gaudin's  Process  (1869). 

Gaudin  f  reduces  aluminium  by  a  process  to  which  he  ap- 
plies the  somewhat  doubtful  title  of  economic.  He  melts  to- 
gether equal  parts  of  cryolite  and  sodium  chloride,  and  traverses 
the  fused  mass  by  a  galvanic  current.  Fluorine  is  evolved  at 
the  positive  pole,  while  aluminium  accumulates  at  the  negative. 

The  great  difficulties  in  such  a  process  are  the  obtaining  of 
suitable  vessels  to  withstand  the  corrosion  of  the  bath,  the  great 
inconvenience  of  the  escaping  fluoride  gas,  and  the  increase  of 
resistance  due  to  the  change  of  composition  of  the  bath.  It 
would  need  several  additional  patents  to  render  this  process 
operative,  without  mentioning  economy. 

Kagensbusch' s  Process  (1872). 

Kagensbusch,!  of  Leeds,  proposes  to  melt  clay  with  fluxes, 
then  adding  zinc  or  a  like  metal  to  pass  an  electric  current 
through  the  fused  mass,  isolating  an  alloy  of  aluminium  and 
the  metal,  from  which  the  foreign  metal  may  be  removed  by 
distillation,  sublimation,  or  cupellation. 

If  the  patentee  had  used  pure  alumina  instead  of  clay,  he 
might  have  produced  some  aluminium  by  his  process,  but  the 
silicon  in  the  clay  would  get  into  the  zinc  in  larger  proportion 

*  English  Patent,  1862,  No.  264. 
t  Moniteur  Scientifique,  xi.,  62. 
X  English  Patent,  1872,  No.  481 1. 


than  the  aluminium,  rendering  the  succeeding  operations  for 
obtaining  pure  aluminium  impossible. 

Berthaut's  Proposition  (1879). 

Up  to  this  time  all  the  proposed  electric  processes  were 
confined  to  the  use  of  a  galvanic  current,  the  cost  of  obtaining 
which  was  a  summary  bar  to  all  ideas  of  economical  produc- 
tion. About  this  period  dynamo-electric  machines  were  being 
introduced  into  metallurgical  practice,  and  Berthaut  is  the  first 
we  can  find  who  proposes  their  use  in  producing  aluminium. 
The  process  which  he  patented  *  is  otherwise  almost  identical 
with  Le  Chatellier's, 

Grdtzel's  Process  (1883). 

This  process  f  has  little  claim  to  originality,  except  in  the 
details  of  the  apparatus.  A  dynamo-electric  current  is  used, 
the  electrolyte  is  fused  cryolite  or  double  chloride  of  aluminium 
and  sodium,  and  the  anodes  are  of  pressed  carbon  and  alumina 
— none  of  which  points  are  new.  However,  the  use  of  melting 
pots  of  porcelain,  alumina,  or  aluminium,  and  making  them  the 
negative  electrode,  are  points  in  which  innovations  are  made. 

In  a  furnace  are  put  two  to  five  pots,  according  to  the  power 
of  the  dynamo  used,  each  pot  having  a  separate  grate.  The 
pots  are  preferably  of  metal,  cast-steel  is  used,  and  form  the 
negative  electrodes.  The  positive  electrode,  K  (Fig.  29),  can 
be  made  of  a  mixture  of  anhydrous  alumina  and  carbon  pressed 
into  shape  and  ignited.  A  mixture  of  alumina  and  gas-tar 
answers  very  well ;  or  it  can  even  be  made  of  gas-tar  and  gas- 
retort  carbon.  During  the  operation  little  pieces  of  carbon  fall 
from  it  and  would  contaminate  the  bath,  but  are  kept  from 
doing  so  by  the  mantle  G.  This  isolated  vessel,  G,  is  perforated 
around  the  lower  part  at  g,  so  that  the  molten  electrolyte  may 
circulate  through.     The  tube  O'  conducts  reducing  gas  into  the 

*  English  Patent,  1879,  No.  4087. 

t  German  Patent  (D.  R.  P.),  No.  26962  (1883). 



crucible,  which  leaves  by  the  tube  0\  This  reducing  atmos- 
phere is  important,  in  order  to  protect  from  burning  any  metal 
rising  to  the  surface  of  the  bath.  The  chlorine  set  free  at  the 
electrode,  K,  partly  combines  with  the  alumina  in  it,  regenera- 
ting the  bath,  but  some  escapes,  and,  collecting  in  the  upper 
part  of  the  surrounding  mantle,  G,  is  led  away  by  a  tube  con- 

FlG.  29. 

necting  with  it.  Instead  of  making  the  electrode  K  of  carbon 
and  alumina,  it  may  simply  be  of  carbon,  and  then  plates  of 
pressed  alumina  and  carbon  are  placed  in  the  bath  close  to  the 
electrode,  K,  but  not  connected  with  it.  Also,  in  place  of 
making  the  crucible  of  metal  and  connecting  it  with  the  nega- 
tive pole,  it  may  be  made  of  a  non-conducting  material,  clay  or 
the  like,  and  a  metallic  electrode — as,  for  instance,  of  alu- 
minium— plunged  into  the  bath. 

In  a  later  patent,*  Gratzel  states  that  the  bath  is  decomposed 

*  English  Patent;  14325,  Nov.  23,  1885.    U.  S.  Patent,  362441,  May  3,  1887. 


by  a  current  of  comparatively  low  tension  if  magnesium  chloride 
be  present ;  the  chlorides  of  barium,  strontium  or  calcium  act 

Prof.  F.  Fischer*  maintains  as  impracticable  the  use  of  plates 
of  pressed  alumina  and  carbon,  which  can,  further,  only  be 
operative  when  they  are  made  the  positive  electrode,  and  then 
their  electric  resistance  is  too  great.  The  incorporation  into 
them  of  copper  filings,  saturation  with  mercury,  etc.,  give  no 
more  practical  results.  There  are  also  volatilized  at  the  anodes 
considerable  quantities  of  aluminium  chloride,  varying  in 
amount  with  the  strength  of  the  current. 

Large  works  were  erected  near  Bremen  by  the  Aluminium 
und  Magnesiumfabrik  Pt.  Gratzel,  zu  Hemelingen,  in  which 
this  process  was  installed.  License  was  also  granted  to  the 
large  chemical  works  of  Schering,  at  Berlin,  to  operate  it.  R. 
Biedermann,  in  commenting  on  the  process  in  i886,f  stated 
that  the  results  obtained  so  far  were  not  fully  satisfactory,  but 
the  difficulties  which  had  been  met  were  of  a  kind  which  would 
certainly  be  overcome.  They  were  principally  in  the  polariza- 
tion of  the  cathode,  by  which  a  large  part  of  the  current  was 
neutralized.  By  using  proper  depolarizing  substances  this  dif- 
ficulty would  be  removed.  The  utilization  of  the  chlorine 
evolved  would  also  very  much  decrease  the  expenses.  A  more 
suitable  slag,  which  collected  the  aluminium  together  better, 
was  also  desirable.  Finally,  the  metal  produced  was  somewhat 
impure,  taking  up  iron  from  the  iron  pots  and  silicon  from  the 
clay  ones,  to  obviate  which  Biedermann  recommended  the  use 
of  lime  or  magnesia  vessels. 

Prof.  Fischer,  as  we  have  seen,  maintained  the  uselessness  of 
Gratzel's  patent  claims,  and  his  later  expression  of  this  opinion 
in  1887  drew  a  reply  from  A.  Saarburger,  Jdirectorof  the  works 
at  Hemehngen,  to  the  effect  that  since  October,  1887,  they  had 

*  Wagner's  Jahresbericht,  1884,  p.  1319;    1887,  p.  376. 

fKerl  und  Stohman,  4th  ed.,  p.  725. 

{  Verein  der  Deutsche  Ingenieure,  Jan.  26,  1889. 


abandoned  the  Gratzel  process,  and  were  making  aluminium  at 
present  by  methods  devised  by  Herr  Saarburger;  in  conse- 
quence of  which  fact  the  directors  of  the  company  decided  in 
January,  1888,  to  drop  the  addition  Pt.  Gratzel  from  the  firm 
name.  The  methods  then  in  use  at  Hemelingen  were  kept  secret, 
but  the  author  was  informed  by  a  friend  in  Hamburg  that  they 
were  using  a  modified  Deville  sodium  process.  Herr  Saarbur- 
ger informed  me  in  October,  1888,  that  they  were  producing 
pure  aluminiuin  at  the  rate  of  12  tons  a  year,  besides  a  large 
quantity  sold  in  alloys.  An  attractive  pamphlet  issued  by  this 
firm  set  forth  precautions  to  be  used  in  making  aluminium 
alloys,  together  with  a  digest  of  their  most  important  properties, 
which  we  shall  have  occasion  to  quote  from  later  in  considering 
those  alloys. 

The  sharp  decline  in  the  price  of  aluminium  in  1890  forced 
this  company  out  of  the  aluminium  business. 

Cowles  Bros!  Process. 

Messrs.  E.  H.  and  A.  H.  Cowles  patented  in  the  United 
States  and  Europe  *  an  electric  furnace  and  its  application  for 
producing  aluminium.  Their  patent  claims  "  reducing  an  alu- 
minium compound  in  company  with  a  metal  in  presence  of  car- 
bon in  a  furnace  heated  by  electricity ;  the  alloy  of  aluminium 
and  the  metal  formed  being  further  treated  to  separate  out  the 
aluminium."  The  history  of  the  development  of  this  process 
having  already  been  sketched,  we  will  proceed  to  describe  the 
details  of  its  operation.  The  first  public  description  was  given 
in  two  papers,  one  read  before  the  American  Association  for  the 
Advancement  of  Science  f  by  Prof.  Chas.  F.  Mabery  of  the  Case 
School  of  Applied  Science,  Cleveland,  the  other  before  the 
American  Institute  of  Mining  Engineers  %  by  Dr.  T.  Sterry 
Hunt,  of  Montreal. 

*  U.  S.  Patents  324658,  324659,  Aug.  18,  1885;  English  Patent  9781,  same  date; 
German  Patent  33672. 

t  Ann  Arbor  Meeting,  Aug.  28,  1885. 
X  Halifax  Meeting,  Sept.  16,  1885. 


Prof.  Mabery  said  in  his  paper :  "  Some  time  since,  the  Messrs. 
Cowles  conceived  the  idea  of  obtaining  a  continuous  high  tem- 
perature on  an  extended  scale  by  introducing  into  the  path  of 
an  electric  current  some  material  that  would  afford  the  requi- 
site resistance,  thereby  producing  a  corresponding  increase  in 
the  temperature.  After  numerous  experiments,  coarsely  pul- 
verized carbon  was  selected  as  the  best  means  for  maintaining 
an  invariable  resistance,  and  at  the  same  time  as  the  most 
available  substance  for  the  reduction  of  oxides.  When  this 
material,  mixed  with  the  oxide  to  be  reduced,  was  made  a  part 
of  the  electric  circuit,  inclosed  in  a  fire-clay  retort,  and  sub- 
jected to  the  action  of  a  current  from  a  powerful  dynamo,  not 
only  was  the  oxide  reduced,  but  the  temperature  increased  to 
such  an  extent  that  the  whole  interior  of  the  retort  fused  com- 
pletely. In  other  experiments  lumps  of  lime,  sand,  and  corun- 
dum were  fused,  with  a  reduction  of  the  corresponding  metal ; 
on  cooling,  the  lime  formed  large,  well-defined  crystals,  the 
corundum  beautiful  red-green  and  blue  octahedral  crystals. 
Following  up  these  results,  it  was  soon  found  that  the  intense 
heat  thus  produced  could  be  utilized  for  the  reduction  of  oxides 
in  large  quantities,  and  experiments  were  next  tried  on  a  large 
scale  with  the  current  from  a  fifty  horse-power  dyamo.  For 
the  protection  of  the  walls  of  the  furnace,  which  were  of  fire- 
brick, a  mixture  of  ore  and  coarsely  pulverized  gas-carbon  was 
made  a  central  core,  and  was  surrounded  on  the  side  and  bot- 
tom by  fine  charcoal,  the  current  following  the  lesser  resistance 
of  the  core  from  carbon  electrodes  inserted  in  the  ends  of  the 
furnace  in  contact  with  the  core.  The  furnace  was  charged  by 
first  filling  it  with  charcoal,  making  a  trough  in  the  centre,  and 
filling  this  with  the  ore  mixture,  the  whole  being  covered  with 
a  layer  of  coarse  charcoal.  The  furnace  was  closed  on  top 
with  fire-brick  slabs  containing  tivo  or  three  holes  for  the 
escape  of  the  gaseous  products  of  the  reduction,  and  the  whole 
furnace  was  made  air-tight  by  luting  with  fire-clay.  Within  a 
few  minutes  after  starting  the  dynamo,  a  stream  of  carbonic 
oxide  issued  through  the  openings,  burning  usually  with  a  flame 


eighteen  inches  high.  The  time  required  for  complete  reduc- 
tion was  ordinarily  about  an  hour.  Experience  has  already 
shown  that  aluminium,  silicon,  boron,  manganese,  sodium  and 
potassium  can  be  reduced  from  their  oxides  with  ease.  In  fact, 
there  is  no  oxide  that  can  withstand  the  temperature  attainable 
in  this  furnace.  Charcoal  is  changed  to  graphite;  does  this 
indicate  fusion?  As  to  what  can  be  accomplished  by  convert- 
ing enormous  electrical  energy  into  heat  within  narrow  limits, 
it  can  only  be  said  that  it  opens  the  way  into  an  extensive  field 
of  pure  and  applied  chemistry.  It  is  not  difficult  to  conceive 
of  temperature  limited  only  by  the  power  of  carbon  to  resist 

"  Since  the  motive  power  is  the  chief  expense  in  accomplish- 
ing reductions  by  this  method,  its  commercial  success  is 
closely  connected  with  obtaining  power  cheaply.  Realizing 
the  importance  of  this  point,  Messrs.  Cowles  have  purchased  at 
Lockport,  N.  Y.,  a  water-power  where  they  can  utilize  I200 
horse-power.  An  important  feature  in  the  use  of  these  furnaces 
from  a  commercial  standpoint  is  the  slight  technical  skill  re- 
quired in  their  manipulation.  The  four  furnaces  operated  in 
the  experimental  laboratory  at  Cleveland  are  in  charge  of  two 
young  men,  who  six  months  ago  knew  absolutely  nothing 
of  electricity.  The  products  at  present  manufactured  are 
the  various  grades  of  aluminium  bronze,  made  from  a  rich 
furnace  product  obtained  by  adding  copper  to  the  charge  of 
ore.  Aluminium  silver  is  also  made ;  and  a  boron  bronze  may 
be  prepared  by  the  reduction  of  boracic  acid  in  contact  with 
copper,  while  silicon  bronze  is  made  by  reducing  silica  in  con- 
tact with  copper.  As  commercial  results  may  be  mentioned 
the  production  in  the  experimental  laboratory,  which  averages 
50  lbs.  of  10  per  cent,  aluminium  bronze  daily,  which  can  be 
supplied  to  the  trade  in  large  quantities  on  the  basis  of  $5  per 
lb.  for  the  aluminium  contained,  the  lowest  market  quotation  of 
aluminium  being  now  $15  per  lb." 

Dr.  Hunt  stated  further  that  if  the  mixture  consisted  of  alu- 
mina and  carbon  only,  the  reduced  metal  volatilized,  part  es- 


caping  into  the  air  and  burning  to  alumina,  part  condensing  in 
the  upper  layer  of  charcoal,  affording  thus  crystalline  masses  of 
nearly  pure  aluminium  and  yellow  crystals  supposed  to  be  a 
compound  of  aluminium  with  carbon.  Great  loss  was  met  in 
collecting  this  divided  metal  into  an  ingot,  so  that  only  small 
quantities  were  really  obtained.  To  gather  all  the  aluminium 
together,  a  metal  such  as  copper  was  added,  thus  producing  an 
alloy  with  15  to  20  per  cent,  of  aluminium ;  on  substituting 
this  alloy  for  pure  copper  in  another  operation,  an  alloy  with 
over  30  per  cent,  of  aluminium  was  obtained. 

Dr.  Hunt,  in  a  later  paper,*  stated  that  pure  aluminium  has 
been  obtained  in  this  process  by  first  producing  in  the  furnace 
an  alloy  of  aluminium  and  tin,  then  melting  this  with  lead, 
when  the  latter  takes  up  the  tin  and  sinks  with  it  beneath 
the  aluminium.  He  also  stated  that  in  the  early  experiments  a 
dynamo  driven  by  a  30  horse-power  engine  yielded  a  daily  out- 
put of  50  lbs.  of  10  per  cent,  aluminium  bronze,  but  with  a 
larger  machine  the  output  was  proportionally  much  greater. 
In  the  latest  practice,  one-half  cent  per  horse-power  per  hour 
is  said  to  cover  the  expense  of  working,  making  the  10  per 
cent,  bronze  cost  about  5  cents  per  lb.  over  the  copper  used. 

Various  shapes  of  furnaces  have  been  used  by  the  Cowles 
Bros.,  the  first  described  being  a  rectangular  box,  lined  with 
carbon,  with  the  electrodes  passing  through  the  ends.  Al- 
though two  other  forms  have  been  patented,  we  understand 
that  the  kind  now  used,  aad  which  is  described  at  length  in  Mr. 
Thompson's  paper,  is  also  of  the  oblong,  horizontal  style. 
Chas.  S.  Bradley  and  Francis  B.  Crocker,  of  New  York,  patented 
and  assigned  to  the  Cowles  Electric  Smelting  Company,f  the 
use  of  a  retort,  composed  of  conducting  material,  surrounded 
by  a  substance  which  is  a  poor  conductor  of  heat,  and  having 
inside  a  mixture  of  charcoal  and  the  ore  to  be  heated.  Electric 
connection  being  made  with  the  ends  of  the  retort,  the  walls  of 

♦National  Academy  of  Science,  Washington  Meeting,  April  30,  1886. 
tU.  S.  Patent  335499,  Feb.  j.,  1886. 


the  retort  and  the  material  in  it  are  included  in  the  circuit  and 
constitute  the  greater  part  of  the  resistance.  The  retort  may 
be  stoppered  at  each  end  during  the  operation,  and  the  heating 
thus  performed  in  a  reducing  atmosphere.  Mr.  A.  H.  Cowles 
devised  a  style  of  furnace  adapted  for  continuous  working  and 
utilizing  the  full  current  of  a  dynamo  of  the  largest  size.f  The 
electrodes  are  tube-shaped  and  placed  vertically.  The  positive 
pole  is  above,  and  is  surmounted  by  a  funnel  in  which  the 
mixture  for  reduction  is  placed.  The  regular  delivery  of  the 
mixture  is  facilitated  by  a  carbon  rod,  passing  through  the 
cover  of  the  funnel,  which  is  serrated  on  the  end  and  can  be 
worked  up  and  down.  The  melted  alloy  produced,  with  any 
slag,  passes  down  through  the  negative  electrode.  The  dis- 
tance between  the  poles  can  be  regulated  by  moving  the  upper 
one,  and  the  whole  is  inclosed  in  a  fire-brick  chamber.  The 
space  between  the  electrodes  and  the  walls  is  filled  with  an  iso- 
lating material,  which  is  compact  around  the  lower  electrode 
but  coarse  grained  around  the  upper  to  facilitate  the  escape  of 
the  gases  produced.  The  chamber  is  tightly  closed  excepting 
a  small  tube  for  the  escape  of  gas. 

A  very  complete  description  of  the  Cowles  process  was  given 
by  Mr,  W.  P.  Thompson  (agent  for  the  Cowles  Co.  in  England) 
in  a  paper  read  before  the  Liverpool  Section  of  the  Society  of 
Chemical  Industry. f  He  describes  the  process  as  then  carried 
on  in  Lockport,  the  dynamo  used  being  a  large  Brush  machine 
weighing  2J^  tons  and  consuming  about  lOO  horse-power  in 
being  driven  at  900  revolutions  per  minute. 

"  Conduction  of  the  current  of  the  large  dynamo  to  the  furnace 
and  back  is  accompHshed  by  a  complete  metallic  circuit,  except 
where  it  is  broken  by  the  interposition  of  the  carbon  electrodes 
and  the  mass  of  pulverized  carbon  in  which  the  reduction  takes 
place.  The  circuit  is  of  13  copper  wires,  each  0.3  inch  in  dia- 
meter.    There  is  likewise  in  the  circuit  an  ampere  meter,  or  am- 

*  English  Patent  4664  (1887). 
.f  Journal  of  the  Society  of  Chemical  Industry,  April  29,  1886. 



meter,  through  whose  helix  the  whole  current  flows,  indicating 
the  total  strength  of  the  current  being  used.  This  is  an  import- 
ant element  in  the  management  of  the  furnace,  for,  by  the  posi- 
tion of  the  finger  on  the  dial,  the  furnace  attendant  can  tell  to  a 
nicety  what  is  being  done  by  the  current  in  the  furnace.  Be- 
tween the  ammeter  and  the  furnace  is  a  resistance  coil  of  Ger- 
man silver  kept  in  water,  throwing  more  or  less  resistance  into 
the  circuit  as  desired.  This  is  a  safety  appliance  used  in 
changing  the  current  from  one  furnace  to  another,  or  to  choke 
off  the  current  before  breaking  it  by  a  switch. 

"The  furnace  (see  Figs.  30,  31,  32)  is  simply  a  rectangular 

Fig.  30. 

box.  A,  one  foot  wide,  five  feet  long  inside,  and  fifteen  inches 
deep,  made  of  fire-brick.  From  the  opposite  ends  through  the 
pipes  BB  the  two  electrodes  CC  pass.  The  electrodes  are  im- 
mense electric-light  carbons  three  inches  in  diameter  and  thirty 

Fig.  31. 


inches  long.  If  larger  electrodes  are  required,  a  series  this  size 
must  be  used  instead,  as  so  far  all  attempts  to  make  larger  car- 
bons that  will  not  disintegrate  on  becoming  incandescent  have 
failed.     The  ends  of  the  carbons  are  placed  within  a  few  inches 



of  each  other  in  the  middle  of  the  furnace,  and  the  resistance 
coil  and  ammeter  are  placed  in  the  circuit.  The  ammeter  regis- 
ters 50  to  2000  amperes.  These  connections  made,  the  furnace 
is  ready  for  charging. 

"  The  walls  of  the  furnace  must  first  be  protected,  or  the  in- 
tense heat  would  melt  the  fire-brick.  The  question  arose,  what 
would  be  the  best  substance  to  line  the  walls.  Finely  powdered 
charcoal  is  a  poor  conductor  of  electricity,  is  considered  infusi- 
ble and  the  best  non-conductor  of  heat  of  all  solids.  From 
these  properties  it  would  seem  the  best  material.     As  long  as 

Fig.  32. 


air  is  excluded  it  will  not  burn.  But  it  is  found  that  after  using 
pure  charcoal  a  few  times  it  becomes  valueless ;  it  retains  its 
woody  structure,  as  is  shown  in  larger  pieces,  but  is  changed 
to  graphite,  a  good  conductor  of  electricity,  and  thereby  tends 
to  diffuse  the  current  through  the  lining,  heating  it  and  the  walls. 
The  fine  charcoal  is  therefore  washed  in  a  solution  of  Hme- 
water,  and  after  drying  each  particle  is  insulated  by  a  fine 
coating  of  lime.  The  bottom  of  the  furnace  is  now  filled  with 
this  lining  about  two  or  three  inches  deep.  A  sheet-iron  gauge 
is  then  placed  along  the  sides  of  the  electrodes,  leaving  about 
two  inches  between  them  and  the  side  walls,  in  which  space 
more  of  the  charcoal  is  placed.  The  charge  E,  consisting  of 
about  25  pounds  of  alumina,  iii  its  native  form  as  corundum,  12 


pounds  of  charcoal  and  carbon,  and  50  pounds  of  granulated 
copper,  is  now  placed  within  the  gauge  and  spread  around  the 
electrodes  to  within  a  foot  of  each  end  of  the  furnace.  For 
making  iron  alloy  where  silicon  also  is  not  harmful,  bauxite  or 
various  clays  containing  iron  and  silica  may  be  used  instead  of 
the  pure  alumina  or  corundum.  In  place  of  granulated  cop- 
per, a  series  of  short  copper  wires  or  bars  can  be  placed  parallel 
to  each  other  and  transverse  to  the  furnace,  among  the  alumina 
and  carbon,  it  being  found  that  where  grains  are  used  they 
sometimes  fuse  together  in  such  a  way  as  to  short-circuit  the 
current.  After  this,  a  bed  of  charcoal,  F,  the  granules  of  which 
vary  in  size  from  a  chestnut  to  a  hickory,  is  spread  over  all, 
and  the  gauge  drawn  out.  This  coarse  bed  of  charcoal  above 
the  charge  allows  free  escape  of  the  carbonic  oxide  generated  in 
the  reduction.  The  charge  being  in  place,  an  iron  top,  G, 
lined  with  fire-brick,  is  placed  over  the  whole  furnace  and  the 
crevices  luted  to  prevent  access  of  air.  The  brick  of  the  walls 
insulate  the  cover  from  the  current. 

"  Now  that  the  furnace  is  charged,  and  the  cover  luted  down, 
it  is  started.  The  ends  of  the  electrodes  were  in  the  beginning 
placed  close  together,  as  shown  in  the  longitudinal  section,  and 
for  this  cause  the  internal  resistance  of  the  furnace  may  be  too 
low  for  the  dynamo,  and  cause  a  short  circuit.  The  operator, 
therefore,  puts  sufficient  resistance  into  the  circuit,  and  by 
watching  the  ammeter,  and  now  and  then  moving  one  of  the 
electrodes  out  a  trifle,  he  can  prevent  undue  short-circuiting  in 
the  beginning  of  the  operation.  In  about  ten  minutes,  the  cop- 
per between  the  electrodes  has  been  melted  and  the  latter  are 
moved  far  enough  apart  so  that  the  current  becomes  steady. 
The  current  is  now  increased  till  1300  amperes  are  going 
through,  driven  by  50  volts.  Carbonic  oxide  has  already  com- 
menced to  escape  through  the  two  orifices  in  the  top,  where  it 
burns  with  a  white  flame.  By  slight  movements  outward  of  the 
electrodes  during  the  coming  five  hours,  the  internal  resistance 
in  the  furnace  is  kept  constant,  and  at  the  same  time  all  the 
different  parts  of  the  charge  are  brought  in  turn  into  the  zone 


of  reduction.  At  the  close  of  the  run  the  electrodes  are  in  the 
position  shown  in  the  plan,  the  furnace  is  shut  down  by  placing 
a  resistance  in  the  circuit,  and  then  the  current  is  switched  into 
another  furnace  charged  in  a  similar  manner.  It  is  found  that 
the  product  is  larger  if  the  carbons  are  inclined  at  angles  of  30° 
to  the  horizontal  plane,  as  in  Fig.  33. 

Fig.  33- 


"  This  regulating  of  the  furnace  by  hand  is  rather  costly  and 
unsatisfactory.  Several  experiments  have  therefore  been  tried 
to  make  it  self-regulating,  and  on  January  26,  1886,  a  British 
patent  was  applied  for  by  Cowles  Bros,  covering  an  arrange- 
ment for  operating  the  electrodes  by  means  of  a  shunt  circuit, 
electro-magnet,  and  vibrating  armature.  Moreover,  if  the  elec- 
trodes were  drawn  back  and  exposed  to  the  air  in  their  highly 
heated  state,  they  would  be  rapidly  wasted  away.  To  obviate 
this,  Messrs.  Cowles  placed  what  may  be  called  a  stufifiing-box 
around  them,  consisting  of  a  copper  box  filled  with  copper  shot. 
The  wires  are  attached  to  the  boxes  instead  of  the  electrodes. 
The  hot  electrodes  as  they  emerge  from  the  furnace  first  en- 
counter the  shot,  which  rapidly  carry  off  the  heat,  and  by  the 
time  they  emerge  from  the  box  they  are  too  cool  to  be  oxidized 
by  contact  with  the  air. 

"  Ninety  horse-power  have  been  pumped  into  the  furnace  for 
five  hours.  At  the  beginning  of  the  operation  the  copper  first 
melted  in  the  centre  of  the  furnace.  There  was  no  escape  for 
the  heat  continually  generated,  and  the  temperature  increased 
until  the  refractory  corundum  melted,  and  being  surrounded  on 
all  sides  by  carbon,  gave  up  its  oxygen.  This  oxygen,  uniting 
with  the  carbon  to  form  carbonic  oxide,  has  generated  heat 


which  certainly  aids  in  the  process.  The  copper  has  had  noth- 
ing to  do  with  the  reaction,  as  it  will  take  place  in  its  absence. 
Whether  the  reaction  is  due  to  the  intense  heat  or  to  electric 
action  it  is  difficult  to  say.  If  it  be  electric,  it  is  Messrs.  Cowles' 
impression  that  we  have  here  a  case  where  electrolysis  can  be 
accomplished  by  an  alternating  current,  although  it  has  not 
been  tried  as  yet.  Were  the  copper  absent,  the  aluminium  set 
free  would  now  absorb  carbon,  and  become  a  yellow  crystal- 
line carbide  of  aluminium ;  but,  instead  of  that,  the  copper  has 
become  a  boiling,  seething  mass,  and  the  bubblings  of  its  vapors 
may  distinctly  be  heard.  The  vapors  probably  rise  an  inch  or 
two,  condense,  and  fall  back,  carrying  with  them  the  freed  alu- 
minium. This  continues  until  the  current  is  taken  ofif  the  fur- 
nace, when  we  have  the  copper  charged  with  1 5  to  30  per  cent., 
and  in  some  cases  as  high  as  40  per  cent,  of  its  weight  of  alu- 
minium, and  a  little  silicon.  After  cooling  the  furnace  this 
rich  alloy  is  removed.  A  valuable  property  of  the  fine  charcoal 
is  that  the  metal  does  not  spread  and  run  through  the  inter- 
stices, but  remains  as  a  liquid  mass,  surrounded  below  and  on 
the  sides  by  fine  charcoal,  which  sustains  it  just  as  flour  or 
other  fine  dust  will  sustain  drops  of  water  for  considerable 
periods,  without  allowing  them  to  sink  in.  The  alloy  is  white 
and  brittle.  This  metal  is  then  melted  in  an  ordinary  crucible 
furnace,  poured  into  large  ingots,  the  amount  of  aluminium  in 
it  determined  by  analysis,  again  melted,  and  the  requisite 
amount  of  copper  added  to  make  the  bronze  desired. 

"Two  runs  produce  in  ten  hours'  average  work  100  pounds 
of  white  metal,  from  which  it  is  estimated  that  Cowles  Bros.,  at 
Lockport  are  producing  aluminium  in  its  alloys  at  a  cost  of 
about  40  cents  per  lb.  The  Cowles  Company  will  shortly  have 
1200  horse-power  furnaces.  With  a  larger  furnace  there  is  no 
reason  why  it  should  not  be  made  to  run  continuously,  like  the 
ordinary  blast  furnace. 

"  In  place  of  the  copper  any  non-volatile  metal  may  be  used 
as  a  condenser  to  unite  with  any  metal  it  may  be  desired  to 
reduce,  provided,  of  course,  that  the  two  metals  are  of  such  a 


nature  that  they  will  unite  at  this  high  temperature.  In  this 
way  aluminium  may  be  alloyed  with  iron,  nickel,  silver,  tin  or 
cobalt.  Messrs.  Cowles  have  made  alloys  containing  50  alu- 
minium to  50  of  iron,  30  aluminium  to  70  of  copper,  and  25 
aluminium  to  75  of  nickel.  Silicon  or  boron  or  other  rare 
metals  may  be  combined  in  the  same  way,  or  tertiary  alloys 
may  be  produced ;  as,  for  instance,  where  fire-  clay  is  reduced 
in  presence  of  copper  we  obtain  an  alloy  of  aluminium,  silicon 
and  copper." 

Soon  after  Mr.  Thompson's  description,  the  plant  at  Lock- 
port  was  increased  by  the  addition  of  the  largest  dynamo  up  to 
that  time  constructed,  built  by  the  Brush  Electric  Company, 
and  dubbed  the  "  Colossus."  This  machine  weighs  almost  ten 
tons,  and  when  driven  at  423  revolutions  per  minute  it  pro- 
duced a  useful  current  of  3400  amperes  at  a  tension  of  68  volts, 
or  at  405  revolutions  produced  a  current  of  3200  amperes  with 
83  volts  electro-motive  force,  indicating  249,000  Watts  or  334 
electric  horse-power.  The  steam  engine  was,  in  the  latter  case, 
developing  nearly  400  horse-power,  and  could  not  supply 
more ;  it  was  judged  that  the  dynamo  could  have  been  driven 
to  300,000  Watts  with  safety.  The  first  run  with  this  machine 
was  made  in  September,  1886.  The  furnaces  used  for  this  cur- 
rent are  of  the  same  style  as  that  described  by  Mr.  Thompson, 
but  are  larger,  the  charge  being  60  lbs.  of  corundum,  60  lbs.  of 
granulated  copper,  30  lbs.  of  coarse  charcoal  besides  the  pulver- 
ized lime-coated  charcoal  used  in  packing.  The  operation  of 
reducing  this  charge  takes  about  two  hours.  As  soon  as  the 
operation  is  finished  the  current  is  switched  off  into  another 
furnace  prepared  and  charged,  so  that  the  dynamo  is  kept  work- 
ing continuously.  In  1888,  the  Cowles  Company  had  two  of 
these  large  dynamos  in  operation,  and  eight  furnaces  in  use. 
With  two-hour  runs  a  furnace  is  tapped  every  hour,  producing 
about  80  lbs.  of  bronze  averaging  18  per  cent,  of  aluminium. 
The  capacity  of  the  plant  is,  therefore,  about  i}i  tons  of  10 
per  cent,  bronze  per  day.  Their  alloys  were  sold  in  1890  on 
the  basis  of  $2.50  per  lb.  for  the  contained  aluminium. 



The  Cowles  Syndicate  Company,  of  England,  located  at 
Stoke-on-Trent,  have  set  up  a  large  plant  at  Milton,  where,  pro- 
fiting by  the  experience  of  the  parent  concern  in  America,  still 
larger  electric  currents  are  used,  these  being  found  more  eco- 
nomical. The  dynamo  in  use  at  this  works  was  built  by  Cromp- 
ton,  and  supplies  a  current  of  5000-6000  amperes  at  50  to  60 
volts.  There  are  two  furnace-rooms,  each  containing  six  fur- 
naces, aluminium  and  silicon  bronze  being  produced  in  one 
room,  and  ferro-aluminium  in  the  other.  The  furnaces  used 
measure  60  by  20  by  36  inches,  inside  dimensions,  and  differ 
from  those  previously  shown  by  having  the  electrodes  inclined 
at  an  angle  of  about  30°.    (See  Figs.  33,  34).     The  electrodes 


used  are  formed  by  bundling  together  9  carbon  rods,  each  2^^ 
inches  in  diameter,  each  electrode  weighing  20  lbs.  More  re- 
cently larger  carbons  have  been  obtained,  3  inches  in  diameter, 
and  an  electrode  formed  of  five  of  these  weighs  36  lbs.  The 
furnace  is  charge^  as  previously  described. 

The  current  is  started  at  3000  amperes,  gradually  increasing 
to  5000  during  the  first  half  hour,  and  then  keeping  steady 
until  the  run  is  ended,  which  is  about  one  and  a  half  hours 
from  starting.  The  product  of  each  run  is  about  100  lbs.  of 
raw  bronze  containing  15  to  20  per  cent,  of  aluminium.  The 
return  is  said  to  average   i  lb.  of  contained  aluminium  per  18 


electric  horse-power  hours,  or  ij^  lbs.  per  electric  horse- 
power per  day.  The  works  produce  about  200  lbs.  of  alumin- 
ium contained  in  alloys  per  day.  The  raw  bronze  is  stacked 
until  several  runs  have  accumulated,  then  a  large  batch  is  melted 
at  once  in  a  reverberatory  furnace,  refined  and  diluted  to  the 
proportion  of  aluminium  required  by  adding  pure  copper. 

The  Cowles  Company,  both  in  England  and  America,  pro- 
duce six  standard  grades  of  bronze  as  follows : 

'Special"  A. 








cent,  of  aluminium 


(                    it 


it                    It 


t                    ti 

t                    it 
i                    ti 

Their  ferro-aluminium  is  sold  with  usually  5  to  7  per  cent. 
of  aluminium,  but  10,  13,  and  15  per  cent,  is  furnished  if 
asked  for. 

Products  of  the  Cowles  furnace. — Dr.  W..  Hampe  obtained  the 
following  results  on  analyzing  a  sample  of  Cowles  Bros.'  10  per 
cent,  bronze : 

Copper 90.058 

Aluminium 8.236 

Silicon 1.596 

Carbon. 0.104 

Magnesium 0.019 

Iron trace. 


A  sample  of  10  per  cent,  bronze,  made  in  the  early  part  of 
1886,  and  analyzed  in  the  laboratory  of  the  Stevens  Institute, 
showed — 

Copper 88.0 

Aluminium 6.3 

Silicon 6.5 

but  it  is  evident  that  the  percentage  of  silicon  has  since  then 
been  lowered. 


The  ferro-aluminium  used  by  Mr.  Keep  in  his  tests  on  cast- 
iron  was  furnished  by  the  Cowles  Company,  and  analyzed — 

Aluminium I  ^4^ 

Silicon  , 3'86 

A  sample  shipped  to  England  in  December,  1886,  contained — 

Iron 86.69 

Combined  carbon I.oi 

Graphitic  carbon 1.9' 

Total 2.92 

Silicon 2.40 

Manganese 0.31 

Aluminium 6.50 

Copper 1.05 

Sulphur 0.00 

Phosphorus 0.13 
















The  copper  in  this  alloy  was  present  by  accident,  the  alloy 
regularly  made  containing  none,  but  the  rest  of  the  analysis 
gives  a  correct  idea  of  the  constitution  of  the  alloy.  Prof. 
Mabery  gives  several  analyses  of  Cowles'  ferro-aluminium : — * 

Iron 85.17 

Aluminium 8.02 

Silicon 2.36 


The  slags  formed  in  the  furnace  in  producing  this  alloy  were 
analyzed  as  follows : — 

Silica 0.78  4.10 

Alumina  (insoluble) 0.20  — 

Lime 28.50  14.00 

Iron 1.50  29.16 

Alumina  (soluble)  -(-  aluminium 38.00  48.70 

Sulphur 0.50  — 

Graphite 5.00  2.60 

Combined  carbon 0.90  0.48 

The  slags  formed  when  producing  bronze  vary  in  composition, 
"American  Chemical  Journal,  1887,  p.  11. 


and  are  usually  crystalline,  with  a  shining,  vitreous  lustre. 
Their  analysis  shows — 

Alumina  (insoluble) 55.30  66.84  — 

Alumina  (soluble)  +  aluminium 21.80  14.20  — 

Lime 3.70  1.44  6.77 

Copper —  3.32  i.oo 

Carbon 0.65 

The  lime  present  probably  existed  as  calcium  aluminate.  These 
slags  contained  only  a  small  amount  of  aluminium,  rarely  any 
iron,  and  were  usually  free  from  silica. 

The  same  chemist  analyzed  a  peculiar  product  sometimes 
formed  in  the  furnace  when  smelting  for  bronze,  in  the  shape 
of  crystalline  masses,  steel-gray  to  bright  yellow  in  color,  semi- 
transparent  and  with  a  resinous  lustre.  These  all  contained 
aluminium,  copper,  silicon  and  calcium  in  various  proportions, 
and  when  exposed  to  the  air  fell  to  powder.     Analyses  gave 

Copper 26.70  35-0°  20.00  — 

Aluminium 66.20  53-30  74.32  15.23 

Silicon 5.00  12.30  2.86  20.55 

Calcium 2.00  0.20  2.86  ^ 

Tin _  _  _  49.26 

99.90      100.80       100.04        85.04 

The  latter  product  was  formed  in  smelting  for  aluminium-tin. 

Prof.  Mabery  also  found  that  the  soot  collecting  at  the  ori- 
fices on  top  of  the  furnace  contained  10  to  12  per  cent,  of  alu- 
minium ;  also  that  when  alumina  and  carbon  alone  were  heated 
and  silica  was  present,  the  aluminium  formed  dissolved  up  to 
10  per  cent,  of  silicon,  which,  on  dissolving  the  aluminium  in 
hydrochloric  acid,  was  left  as  crystalline  or  graphitic  silicon. 

Reactions  in  Cowles'  process. — The  inventors,  themselves, 
claim  "  reduction  in  a  furnace  heated  by  electricity  in  presence 
of  carbon  and  a  metal."  In  their  first  pamphlet  they  say  that 
"  the  Cowles  process  accomplishes  the  reduction  of  alumina  by 
carbon  and  heat."     Professor  Mabery  and  Dr.  Hunt,  already 


quoted,  and  Dr.  Kosman  *  look  at  the  process  in  no  other  light 
than  that  the  electric  current  is  utilized  simply  by  its  conver- 
sion into  heat  by  the  resistance  offered,  and  that  pure  elec- 
trolysis is  either  absent  or  occurs  to  so  small  an  extent  as  to  be 
inappreciable.  Indeed,  if  we  consider  the  arrangement  of  the 
parts  in  the  Cowles  furnace  we  see  every  effort  made  to  oppose 
a  uniform,  high  resistance  to  the  passage  of  the  current  and  so 
convert  its  energy  into  heat,  and  an  entire  absence  of  any  of 
the  usual  arrangements  for  electrolysis.  For  instance,  elec- 
trolysis requires  a  fluid  bath  in  circulation,  so  that  each  ele- 
ment of  the  electrolyte  may  be  continuously  liberated  at  one  of 
the  poles  and  the  presence  of  any  foreign  material,  as  bits  of 
carbon,  between  the  poles  is  to  be  avoided  if  possible,  since 
they  short-circuit  the  current  and  hinder  electrolysis  proper. 
I  think  the  arrangement  of  the  furnace  shows  no  attempt  to 
fulfil  any  of  the  usual  conditions  for  electrolysis,  but  is  one  of 
the  best  arrangements  for  converting  the  energy  of  the  current 
entirely  into  heat.  Dr.  Hampe,  however,  in  spite  of  these 
evident  facts,  draws  the  conclusion  that  because  he  was  unable 
to  reduce  alumina  by  carbon  in  presence  of  copper  at  the  tem- 
perature of  a  Deville  lime-furnace,  that  it  was  therefore  to  be 
assumed  that  even  the  somewhat  higher  temperature  of  the 
electric  furnace  alone  would  be  insufficient  to  accomplish  the 
desired  reaction,  and  hence  the  effect  of  the  electric  arc  must 
be  not  only  electro-thermic  in  supplying  heat,  but  afterwards 
electrolytic,  in  decomposing  the  fused  alumina. 

If  we  figure  out  the  useful  effect  of  the  current,  i.  e.,  the  pro- 
portion of  its  energy  utilized  for  the  purpose  of  reducing  alumina, 
we  find  a  low  figure ;  but  it  is  well  to  note  that  although  the 
power  required  is  one  of  the  main  features  of  this  way  of  reduction, 
yet  this  item  is  so  cheap  at  the  firm's  works  that  it  becomes  a 
secondary  consideration  in  the  economy  of  the  process.  A  300 
horse-power    current    is    equivalent    to    an    expenditure    of 

300 7 — ?__  jg J 000  calories  of  heat  per  hour.     Theoretically, 


*  Stahl  und  Eisen,  Jan.  I 


this  amount  of  heat  would  produce  i^i^  =  261^   kilos  or  58 

pounds  of  aluminium.  However,  about  7  pounds  are  obtained 
in  an  hour's  working,  which  would  show  a  useful  effect  of  12 
per  cent.  This  should  even  be  diminished,  since  no  account 
has  been  taken  of  the  combustion  of  carbon  in  the  furnace  to 
carbonic  oxide.  The  remainder  of  the  heat  account,  probably 
90  per  cent,  of  the  whole,  is  partly  accounted  for  by  the  heat 
contained  in  the  gases  escaping  and  the  materials  withdrawn 
from  the  furnace  (of  which  no  resonable  estimate  can  be  made, 
since  the  question  of  temperatures  is  so  uncertain)  and  the 
large  remainder  must  be  put  down  as  lost  by  radiation  and 
conduction.  As  before  remarked,  water  power  is  obtained  by 
this  company  very  cheaply,  and  even  this  large  loss  does  not 
make  much  show  in  the  cost  of  the  alloy,  yet  the  figures  show 
that  a  much  larger  useful  effect  should  be  possible,  and  it  is  not 
at  all  improbable  that  the  prospect  of  getting  double  or  triple 
the  present  output  from  the  same  plant  is  at  present  inciting 
the  managers  to  fresh  exertions  in  utilizing  the  power  to  better 

Mr.  H.  T.  Dagger's  paper*  on  the  Cowles  process  in  Eng- 
land, states  that  the  product  at  their  Milton  works  is  i  lb.  of 
aluminium  to  18  electric  horse-power  per  hour,  which  would 
show  that  the  dissociation  of  the  alumina  represented  nearly  30 
per  cent,  of  the  energy  of  the  current ;  but  the  data  given  in  the 
body  of  this  gentleman's  paper  (p.  303 )  do  not  seem  to  indi- 
cate so  large  a  return  as  is  stated  above.  Mr.  Dagger,  more- 
over, maintains  the  purely  electro-thermic  action  of  the  current, 
denying  that  any  electrolysis  takes  place  at  all,  citing  an  ex- 
periment with  the  alternating  current  in  one  of  these  furnaces, 
which  produced  as  much  aluminium  per  horse-power  as  did  the 
direct  current.  In  such  an  experiment  electrolysis  must  neces- 
sarily be  absent. 

In  the  discussion  of  Heroult's  alloy  process  it  will  be  shown 
that  in  both  it  and  Cowles'  process  the  largest  part  of  the  re- 

*  British  Association  for  Advancement  of  Science,  Newcastle,  1889. 


duction  must  necessarily  be  performed  by  chemical  and  not  by 
electrolytic  action.  I  do  not  introduce  this  discussion  here, 
since  the  two  processes  resemble  each  other  so  closely  in  the 
reaction  involved  that  they  can  best  be  considered  together. 

Since  1892  no  aluminium  has  been  made  in  England  by  this 
process,  as  the  low  price  of  pure  aluminium  killed  the  market 
for  ready-made  aluminium  alloys.  I  cannot  say  exactly  to 
what  extent  the  Lockport  works  is  running  at  the  present  time, 
but  it  is  probable  that  the  death  of  one  of  the  Cowles  brothers 
in  1893  and  the  sharp  competition  from  pure  aluminium  have 
seriously  hampered  the  business  of  the  American  company. 
At  least,  their  products  are  not  frequently  seen  on  the  market. 

It  may  be  proper  to  interject  here  mention  of  an  unfortunate 
occurrence  in  the  history  of  the  Cowles  Company.  They  sold 
only  aluminium  alloys  until  January,  1891,  when  they  began 
to  advertise  and  sell  pure  aluminium  made,  it  was  said,  by  a 
new  process.  The  Pittsburgh  Reduction  Company  working 
the  Hall  process  were  then  selling  pure  aluminium  as  low  as 
$1.50  per  pound,  while  the  Cowles  Company  commenced  sell- 
ing as  cheap  as  $1.00.  Inside  of  two  months  the  Pittsburgh 
Reduction  Company  instituted  suit  for  infringement  of  the 
Hall  patents,  asking  the  courts  meanwhile  for  a  preliminary 
injunction.  Judge  Ricks,  of  Ohio,  denied  a  complete  injunc- 
tion, but  restrained  the  defendants  from  increasing  the  output 
of  their  plant  during  the  trial  of  the  suit,  or  from  selling  alu- 
minium below  a  price  to  be  named  by  the  complainants.  The 
latter  named  $1.50  per  pound,  and  this  fixed  the  market  price 
for  some  months.  Several  metallurgical  experts  of  wide  repu- 
tation were  engaged  by  both  sides,  and  very  voluminous  testi- 
mony was  taken.  While  the  suit  was  pending,  the  price  of 
aluminium  was  reduced  by  the  European  makers  to  5  marks  a 
kilo  (56  cents  a  pound),  at  which  price  important  quantities 
began  to  be  imported,  and  the  domestic  makers  could  sell  very 
Httle  at  $1.50.  In  consequence,  the  Pittsburgh  Reduction 
Company  notified  the  court  that  it  would  sell  as  low  as  $0.50 
per  pound.     At  this  price,  which  was  very  nearly  the  cost  of 


production,  aluminium  continued  until  the  suit  was  finally  de- 
cided, in  February,  1893,  in  favor  of  the  Hall  process.  Judges 
Taft  and  Ricks  decided  that  the  Cowles  Company  were  using 
the  Hall  process  when  they  electrolyzed  a  bath  of  molten 
cryolite  in  which  alumina  was  dissolved,  and  they  were  ordered 
to  stop  the  infringement  and  to  pay  the  damages  which  it 
might  be  estimated  that  their  infringement  had  caused  the 
complainants'  business. 

Menges'  Patent. 

*  This  inventor  proposes  to  produce  aluminium  or  aluminium 
bronze  by  mixing  aluminous  material  with  suitable  conducting 
material,  such  as  coal,  and  a  cohesive  material,  then  pressing 
into  cylinders  and  baking  hard.  These  strong,  compact  bars 
conduct  electricity,  and  are  to  be  used  like  the  carbon  elec- 
trodes of  electric  lamps  in  a  suitably  inclosed  space. 

Farmer's  Patent. 

M.  G.  Farmer  f  mixes  aluminous  material  with  molasses  or 
pitch,  making  a  paste  which  is  moulded  into  sticks,  burned, 
and  used  as  electrodes,  inclosed  in  a  furnace.  Aluminium  is 
produced  by  the  arc,  and  drops  into  a  crucible  placed  imme- 
diately beneath. 

Several  other  persons  have  patented  exactly  the  same 
method  of  procedure  as  that  indicated  by  Menges  and  Farmer, 
with  the  modification  in  some  cases  of  mixing  iron  or  copper 
turnings  with  the  aluminous  material,  and  having  the  melted 
material  drop  into  a  furnace  kept  hot  by  burning  ordinary  fuel. 
Such  a  method  of  reducing  refractory  ores  was  even  suggested 
as  far  back  as  1853.  None  of  such  processes  are  likely  to  give 
results  sufficiently  economical  for  commercial  use. 

Kleiner's  Process  (1886). 
This  was  devised  by  Dr.  Ed.  Kleiner  of  Zurich,  Switzerland, 

*  German  Patent,  40354  (1887). 

t  English  Patent,  10815,  Aug.  6,  1887. 


and  was  patented  in  most  of  the  European  States.  The  Eng- 
lish patent  is  dated  1886.*  The  first  attempts  to  operate  it 
were  at  the  Rhine  Falls,  Schaffhausen,  and  were  promising 
enough  to  induce  Messrs.  J.  G.  Nethers,  Sons  &  Co.,  pro- 
prietors of  an  iron  works  there,  to  try  to  obtain  water  rights  for 
1500  horse  power,  announcing  that  a  company  (the  Kleiner 
Gesellschaft)  with  a  capital  of  12,000,000  francs,  was  prepared 
to  undertake  the  enterprise  and  build  large  works.  The  pro- 
position is  said  to  have  met  with  strong  opposition  from  the 
hotel-keepers  and  those  interested  in  the  falls  as  an  attraction 
for  tourists,  and  the  government  declined  the  grant,  consider- 
ing that  the  picturesqueness  of  the  falls  would  be  seriously 
afifected.  This  is  the  reason  given  by  those  interested  in  the 
process  for  its  not  being  carried  out  in  Switzerland,  it  being 
then  determined  to  start  a  works  in  some  part  of  England 
where  cheap  coal  could  be  obtained,  and  test  the  process  on  a 
large  scale.  A  small  experimental  plant  was  then  set  up  in  the 
early  part  of  1887  on  Farrington  Road,  London,  where  it  was 
inspected  by  many  scientific  men,  among  them  Dr.  John  Hop- 
kinson,  F.  R.  S.,  who  reported  on  the  quantitative  results 
obtained ;  a  description  of  the  process  as  here  operated  was 
also  written  up  for  "  Engineering."  With  the  co-operation  of 
Major  Ricarde-Seaver  a  larger  plant  was  put  up  at  Hope  Mills, 
Tydesley,  in  Lancashire,  where  the  process  was  inspected  and 
reported  on  by  Dr.  George  Gore,  the  electrician.  After  his 
report  we  learn  that  the  patents  were  acquired  by  the  Alumin- 
ium Syndicate,  Limited,  of  London,  a  combination  of  capitalists 
among  whom  are  said  to  be  the  Rothschilds. 

The  aluminium  compound  used  is  commercial  cryolite.  It 
is  stated  that  the  native  mineral  from  Greenland  contains  on  an 
average,  according  to  Dr.  Kleiner's  analysis,  96  per  cent,  of 
pure  cryolite,  the  remainder  being  moisture,  silica,  oxides  of 
iron  and  manganese.  As  pure  cryolite  contains  13  per  cent, 
of  aluminium,  the  native  mineral  will  contain   12^  per  cent., 

♦English  Patents,  8531,  June  29,  1886,  and  15322,  Nov.  24,  1886. 



all  of  which  Dr.  Kleiner  claims  to  be  able  to  extract.  It  is 
further  remarked  that  as  soon  as  sufificient  demand  arises,  an 
artificial  cryolite  can  be  made  at  much  less  cost  than  that  of  the 
native  mineral,  which  now  sells  at  ;^i8  to  ;^20  a  ton.  The 
rationale  of  the  process  consists  in  applying  the  electric  current 
in  such  a  way  that  a  small  quantity  of  it  generates  heat  and 
keeps  the  electrolyte  in  fusion,  while  the  larger  quantity  acts 
electrolytically.  Dry,  powdered  cryolite  is  packed  around  and 
between  carbon  electrodes  in  a  bauxite-lined  iron  crucible ;   on 

Fig.  35. 

passing  a  current  of  high  tension  (80  to  100  volts)  through  the 
electrodes,  the  cryolite  is  quickly  fused  by  the  heat  of  the  arc 
and  becomes  a  conductor.  As  soon  as  the  electrolyte  is  in 
good  fusion  the  tension  is  lowered  to  50  volts,  the  quantity 
being  about  150  amperes,  the  arc  ceases  and  the  decomposi- 
tion proceeds  regularly  for  two  or  three  hours  until  the  bath  is 



nearly  exhausted.  The  evolved  fluorine  is  said  to  attack  the 
bauxite,  and  by  thus  supplying  aluminium  to  the  bath  extends 
the  time  of  an  operation.  In  the  first  patent  the  negative  car- 
bon was  inserted  through  the  bottom  of  the  melting  cavity,  the 
positive  dipping  into  the  bath  from  above,  (Fig.  35)  but  it  was 
found  that  while  the  ends  of  the  positive  carbon  immersed  in 
the  cryolite  were  unattacked,  the  part  immediately  over  the 
bath  was  rapidly  corroded.  In  the  second  patent,  therefore, 
the  positive  electrode  was  circular  and  entirely  immersed  in 
the  cryolite,  connection  being  made  by  ears  which  projected 
through  the  side  of  the  vessel.     (Fig.  36.)     As  the  carbons 

Fig.  36. 

are  thus  fixed,  the  preliminary  fusion  is  accomplished  by  a 
movable  carbon  rod  suspended  from  above,  passing  through 
the  circular  anode  and  used  only  for  this  purpose.  The  bath 
being  well  fused  and  the  current  flowing  freely  between  the 
fixed  carbons,  the  rod  is  withdrawn.  The  carbons  are  said  to 
be  thus  perfectly  protected  from  corrosion,  and  able  to  serve 
almost  indefinitely.  The  melting  pots  finally  used  were  or- 
dinary black-lead  crucibles,  which  are  not  usually  injured  at  all, 
since  the  fused  part  of  the  cryolite  does  not  touch  them,  and 
they  last  as  many  as  300  fusions.  After  the  operation,  the 
carbons  are   lifted  out  of  the  bath  and  the  contents  cooled. 


When  solid,  the  crucibles  are  inverted  and  the  contents  fall 
out.  This  residue  is  broken  to  coarse  powder,  the  nodules  of 
aluminium  picked  out,  melted  in  a  crucible  and  cast  into  bars. 
The  coarse  powder  is  then  ground  to  fine  dust.  This  powder 
is  more  or  less  alkaline  and  contains  a  greater  or  less  excess  of 
fluoride  of  sodium  in  proportion  to  the  amount  of  aluminium 
which  has  been  taken  out.  If  only  a  small  proportion  of  the 
metal  has  been  extracted  and  the  powder  contains  only  a  small 
excess  of  sodium  fluoride,  it  is  used  again  without  any  pre- 
paration in  charging  the  crucibles ;  but  if  as  much  as  5  or  6 
per  cent,  of  aluminium  has  been  removed  and  the  powder, 
therefore,  contains  a  large  excess  of  sodium  fluoride,  it  is 
washed  with  water  for  a  long  time  to  remove  that  salt,  which 
slowly  dissolves.  The  solution  is  reserved,  while  the  powder 
remaining  is  unchanged  cryolite,  and  is  used  over.  Dr.  Gore 
states  that  if  the  powder,  electrodes  and  crucible  are  perfectly 
dry,  there  is  no  escape  of  gas  or  vapor  during  the  process ; 
but  if  moisture  is  present,  a  small  amount  only  of  fumes  of 
hydrofluoric  acid  appear,  and  that  there  is  no  escape  of  fluorine 
gas  at  any  time.  Dr.  Kleiner  hopes  to  soon  dispense  with  the 
interruption  of  the  process,  washing,  etc.,  by  regenerating 
cryoHte  in  the  crucible  itself  and  so  making  the  process  con- 
tinuous. One  of  the  great  advantages  claimed  is  that  the 
aluminium  is  obtained  in  nodules,  and  not  in  fine  powder;  if  it 
was,  it  could  not  all  be  collected  because  it  is  so  light,  some  of 
it  would  float  upon  the  water  during  the  washing  process  and 
be  lost,  and  even  when  collected  it  could  not  be  dried  and 
melted  without  considerable  loss. 

It  has  been  found  impossible  in  practice  to  obtain  all  the 
aluminium  from  a  given  quantity  of  cryolite  in  less  than  two 
fusions,  for  the  sodium  fluoride  collecting  in  the  bath  hinders 
the  production  of  the  metal.  The  proportion  extracted  by  a 
single  fusion  depends  upon  its  duration.  In  the  operations  at 
Tydesley,  a  fusion  lasting  24  hours  separated  only  2^  per 
cent,  of  aluminium,  whereas  the  cryolite  contained  12^  per 
cent.     At  this  rate,  to  extract  the  whole  in  two  operations  would 


require  two  fusions  of  6o  hours  each.  As  to  the  output,  on  an 
average  a  current  of  38  electric  horse-power  deposited  150 
grammes  of  aluminium  per  hour,  being  a  little  over  3  grammes 
per  horse-power.  Since  a  current  of  50  volts  and  150  amperes, 
such  as  was  stated  above  as  the  current  in  each  pot,  is  equal  to 
50x^50  ^^  j^  electric  H.  P.,  it  is  probable  that  the  38  H.  P.  cur- 
rent mentioned  must  have  been  used  for  four  crucibles.  Now, 
the  output  of  four  crucibles,  each  with  a  current  of  150  amperes, 
should  have  been  0.00009135X150X4=0.0548  gramme  per 
second,  or  197.3  grammes  per  hour;  the  difference  between 
this  and  the  amount  actually  obtained,  or  47.3  grammes,  is  the 
amount  of  aluminium  which  was  produced  and  then  afterwards 
lost  either  as  fine  shot-metal  or  powder,  or  dissolved  again  by 
corroding  elements  in  the  bath.  To  calculate  how  the  output 
of  3  grammes  per  electric  H.  P.  per  hour  compares  with  the 
quantity  of  metal  which  this  amount  of  energy  should  be  able 
to  produce,  we  can  assume  that  since  it  takes  at  most  4  volts  to 
decompose  the  aluminium  fluoride,  the  four  crucibles  would 
consume  16  volts  in  decomposition,  being  sixteen-fiftieths  of 
the  total  voltage  employed.  Since  the  amperes  only  produced 
150  grammes  out  of  197.3  theoretically  possible,  the  efhciency 
over  all  is  only 

16         150        1 

As  to  the  purity  of  the  metal  obtained,  the  process  is  met  at 
the  outset  by  the  silica  and  iron  oxide  in  the  cryolite,  which  are 
probably  all  reduced  with  the  first  few  grammes  of  aluminium 
thrown  down.  This  can  possibly  be  remedied  by  using  a  purer 
artificial  cryolite ;  the  impurities  cannot  generally  be  separated 
from  the  natural  mineral.  Then  there  are  impurities  of  a  simi- 
lar nature  coming  from  the  carbons  used,  and  which  are  gene- 
rally present  if  especial  pains  are  not  taken  to  get  very  pure  ma- 
terials for  making  them.  Dr.  Kleiner's  early  attempts  produced 
metal  of  85  to  95  per  cent,  purity,  but  he  stated  in  1889  that  it 
was  uniformly  95  to  98  per  cent.,  and  being  put  on  the  market  in 


competition  with  other  commercial  brands.  It  appears,  how- 
ever, from  a  consideration  of  the  preceding  data,  that  the  pro- 
cess could  not  produce  aluminium  much  cheaper  than  12  shil- 
lings a  pound,  and  it  was  therefore  abandoned  in  1890.  It  may 
be  observed  that  the  mechanical  arrangements  for  carrying  on 
this  process,  as  above  outlined,  could  not  stand  comparison  with 
the  present  forms  of  apparatus  in  use  by  the  Hall  and  Heroult 

Lossier's  Method. 

*  This  is  a  device  for  decomposing  the  natural  silicates  by 
electricity  and  obtaining  their  aluminium.  The  bath  is  com- 
posed of  pure  aluminium  fluoride  or  of  a  mixture  of  this  salt 
and  an  alkaline  chloride,  and  is  kept  molten  in  a  round  bot- 
tomed crucible  placed  in  a  furnace.  The  electrodes  are  of  dense 
carbon  and  are  separated  in  the  crucible  by  a  partition  reach- 
ing beneath  the  surface  of  the  bath.  The  positive  electrode  is 
furnished  with  a  jacket  or  thick  coating  of  some  aluminium  sili- 
cate plastered  on  moist  and  well  dried  before  use.  When  the 
current  is  passed,  the  aluminium  fluoride  yields  up  its  fluorine  at 
this  pole  and  its  aluminium  at  the  other.  The  fluorine  com- 
bines with  the  aluminium  silicate,  forming  on  the  one  hand  alu- 
minium fluoride,  which  regenerates  the  bath,  on  the  other  silicon 
fluoride  and  carbonic  oxide,  which  escape  as  gases.  The  metal 
liberated  at  the  negative  pole  is  lighter  than  the  fused  bath,  and 
therefore  rises  to  the  surface. 

M.  Grabau  cites  as  one  of  the  recommendations  of  aluminium 
fluoride  for  use  in  his  process  (p.  295),  that  it  is  quite  infusible, 
so  it  would  appear  that  Lossier  has  made  a  mistake  in  suppos- 
ing that  it  could  be  melted  alone  in  a  crucible.  It  would,  how- 
ever, make  a  very  fusible  bath  when  the  alkali  chloride  was 
added.  It  is  probable  that  the  carrying  out  of  this  method 
would  develop  great  trouble  from  the  attacking  of  the  crucible 
by  the  very  corrosive  bath,  the  disintegration  of  the  carbons, 
which  would  cause  much  trouble  at  the  negative  pole  especially, 

*  German  Patent  (D.  R.  P.),  No.  31089. 


and  the  oxidation  of  the  fluid  aluminium  on  the  surface  of  the 
bath.  The  process  has  never  been  attempted  on  a  large  scale, 
and  it  is  very  unlikely  that  it  ever  will  be. 

OmhoKs  Furnace. 

I.  Omholt  and  the  firm  Bottiger  and  Seidler,  of  Gossnitz,  have 
patented  the  following  apparatus  for  the  continuous  electrolysis 
of  aluminium  chloride:* — 

The  bed  of  a  reverberatory  furnace  is  divided  by  transverse 
partitions  into  two  compartments,  in  each  of  which  are  two  re- 
torts semi-circular  in  section,  lying  side  by  side  horizontally 
across  the  furnace,  with  the  circular  part  up.  They  are  sup- 
ported on  refractory  pillars  so  that  their  open  side  is  a  small 
distance  above  the  floor  of  the  furnace.  The  aluminium  com- 
pound being  melted  on  the  hearth,  it  stands  to  the  same  depth 
in  both  retorts,  and  if  the  electrodes  are  passed  through  the 
bottom  of  the  hearth  they  may  remain  entirely  submerged  in 
molten  salt  and  each  under  its  own  retort  cover.  The  metal 
therefore  collects  in  a  liquid  state  under  one  retort  and  the 
chlorine  under  the  other,  both  being  preserved  from  contact  or 
mixture  with  the  furnace  gases  by  the  lock  of  molten  salt.  The 
chlorine  can  thus  be  led  away  by  a  pipe,  and  utilized,  while  the 
aluminium  collects  without  loss,  and  is  removed  at  convenient 

The  great  cost  of  making  aluminium  chloride  will  probably 
prevent  it  ever  being  used  again  in  the  metallurgy  of  alumin- 
ium, but  the  form  of  furnace  described  above  may  possibly  be 
utilized  in  operating  the  decomposition  of  some  other  aluminium 
salt,  such  as  the  double  sulphide  with  soda. 

Minefs  Process  (1887). 
This  consists,  according  to  the  patent  specification, f  in  the 
electrolysis  of  a  mixture  of  sodium  chloride  with  aluminium 
fluoride  or  with  the  separate  or  double  fluorides  of  aluminium 

*  German  Patent  (D.  R.  P.),  No.  34728. 
t  English  Patent,  No.  10057,  July  r8,  1887. 



and  sodium,  melted  in  a  non-metallic  crucible  or  in  a  metallic 
one  inclosed  in  a  thin  refractory  jacket  to  avoid  filtration,  the 
aluminium  fluoride  decomposed  being  regenerated  by  causing 
the  fluorine  vapors  evolved  to  act  on  bauxite  or  alumina 
placed  somewhere  about  the  anode.  The  details  of  the  appar- 
atus and  bath  are  as  follows : — 

Disposition  of  the  Apparatus. — The  pots  or  crucibles  used 
may  be  of  refractory  earth,  plumbago,  or  of  metal,  and  in  cases 
where  an  alloy  is  required  the  crucible  itself  serves  as  an  elec- 
trode. None  of  these,  however,  resist  the  corrosive  power  of 
the  electrolyte  and  would  under  ordinary  conditions  be  quickly 
destroyed.  To  overcome  this  difficulty  two  special  devices  are 
employed.  When  alloys  are  to  be  made  directly,  the  pot  is 
cast  of  the  metal  with  which  the  aluminium  is  to  be  combined. 
It  is  shaped  with  a  sloping  bottom  and  provided  with  a  tap 
hole.  The  pot  is  encased  in  thin  brickwork  and  is  then  made 
the  negative  electrode,  the  positive  being  two  carbon  rods 
dipped  into  the  bath.  As  soon  as  the  current  is  passed  alu- 
minium is  deposited  on  the  walls  of  the  pot,  forming  a  rich 
alloy  with  the  metal  of  which  the  pot  is  made  (iron  or  copper). 
When  this  coating  becomes  sufficiently  rich  in  aluminium,  the 
heat  of  the  bath  melts  it  and  it  trickles  down  and  collects  at  the 
bottom.  After  a  certain  time,  the  alloy  can  be  tapped  out 
regularly  at  intervals  without  interrupting  the  electrolysis.  The 
metal  thus  obtained  is  principally  aluminium  containing  a  few 
per  cent,  of  the  metal  of  the  pot,  which  is  of  no  consequence, 
since  the  end  to  be  finally  attained  is  the  production  of  an  alloy 
with  a  smaller  quantity  of  aluminium.  When  pure  aluminium  is 
to  be  obtained,  an  ingenious  device  is  used  to  protect  the  metal 
from  contamination  by  the  metal  of  the  pot.  Carbon  plates,  A 
and  C  (Fig.  37),  serve  as  anode  and  cathode,  the  cathode  stand- 
ing upright  in  a  small  crucible  placed  upon  a  plate  resting  on 
the  bottom  of  the  pot.  This  crucible  and  plate  are  made  from 
'carbon  blocks  or  from  fused  alumina  or  fluorspar  moulded  into 
the  shape  desired.  As  the  metal  is  set  free  it  trickles  down 
the  cathode  and  is  caught  in  the  crucible  or  cup,  thus  being 



prevented  from  spreading  out  over  the  bottom  of  the  pot.  To 
prevent  the  bath  from  corroding  the  pot,  the  wire  R  is  passed 
from  the  latter  to  the  negative  pole  of  the  circuit.  The  pot  is 
thus  made  part  of  the  negative  electrode,  but  it  is  not  intended 
that  much  of  the  current  should  pass  through  it,  so  a  resistance 
coil  is  interposed  between  it  and  the  battery  or  dynamo,  so  that 

Fig.  37. 

the  derived  current  passing  through  the  sides  of  the  pot  is  only 
5  to  10  per  cent,  of  the  whole  current.  The  effect  of  this  is 
that  a  small  amount  of  aluminium  is  deposited  on  and  alloys 
with  the  sides  of  the  vessel,  which  protects  the  latter  from  cor- 
rosion and  is  only  feebly  acted  upon  by  the  bath.  The  metal 
deposited  in  the  crucible  is  thus  kept  nearly  pure,  while  a  small 
amount  of  alloy  falls  to  the  bottom  of  the  pot  and  is  poured 
out  after  the  crucible  has  been  removed.  When  it  is  wished  to 
obtain  the  purest  aluminium,  the  intensity  of  the  derived  cur- 
rent passing  through  the  pot  is  increased  by  removing  part  of 
the  resistance  interposed  between  it  and  the  negative  wire,  thus 
also   decreasing  the  intensity  of  the  principal  current.     The 


nature  of  the  electrodes  proper  may  be  varied.  For  producing 
pure  aluminium  the  anode  is  carbon,  the  cathode  carbon,  and 
the  pot  either  of  copper  or  iron ;  for  producing  copper  alloys 
the  anode  may  be  either  carbon  or  bright  copper,  and  the 
cathode  (pot)  of  carbon  or  copper;  for  producing  iron  alloys 
the  anode  may  be  either  carbon  or  iron,  while  the  vessel  used 
as  cathode  is  either  of  cast-iron  or  plumbago. 

Composition  and  properties  of  the  baths. — Minet  has  made 
more  careful  electrical  measurements  on  these  fused  baths  than 
any  other  metallurgist,  a  point  of  particular  importance  in  his 
experiments  being  the  accurate  measurement  of  the  tempera- 
tures by  means  of  a  Le  Chatellier  electric  pyrometer.  On  this 
account  his  result^re  a  valuable  contribution  to  the  knowledge 
of  the  present  electrolytic  processes,  and  are  therefore  worth 
repeating  in  extenso.     Minet  first  experimented  with  a  bath  of 

Aluminium-sodium  chloride 40  parts. 

Sodium  chloride 60    " 

He  says  of  the  working  of  this  mixture  that  it  gives  rise  to 
abundant  vapors,  which  are  very  disagreeable.  In  consequence, 
the  bath  becomes  quickly  impoverished  in  aluminium  chloride, 
it  becomes  pasty,  and  can  only  be  liquefied  by  raising  the  tem- 
perature almost  to  the  melting  point  of  sodium  chloride.  It  is 
difficult  under  these  conditions  to  produce  regular  and  continu- 
ous electrolysis. 

Minet  obtained  much  better  results  with  aluminium  fluoride. 
He  mixed  cryolite  with  common  salt  in  the  following  propor- 
tions : 

Cryolite 37-5  parts. 

Sodium  chloride 62.5     " 

giving  a  mixture  whose  formula  would  be  AlFgSNaF  +  6NaCl. 
This  mixture  has  the  following  properties : 

Melting  point 675°  C. 

Vapors  given  off  at 1056°  C. 

Specific  gravity  at  829°  C 1.76 

Specific  resistance  at  870°  C 0.32  ohms. 


The  last  datum  means  that  a  column  of  the  electrolyte  i 
centimetre  square  and  i  centimetre  long  would  give  0.32  ohms 
resistance  to  the  passage  of  the  current.  If  the  section  of  the 
electrolyte  through  which  the  current  passed  averaged  750 
square  centimetres,  and  the  electrodes  averaged  6  centimetres 
apart,  the  total  resistance  of  the  bath  would  be 

0.32  X         ^0.0026  ohms: 

and  if  the  current  was  1 500  amperes,  the  voltage  absorbed  by 
the  electrical  conduction-resistance  of  the  bath  would  be 

0.0026  X  1500  =  3.9  volts. 

The  specific  resistance  was  found  to  decrease  about  0.07  per 
cent,  for  every  degree  rise  of  temperature  above  870°,  or  7  per 
cent,  for  every  lOO  degrees. 

If  this  bath  were  simply  electrolyzed,  fluorine  would  be  dis- 
engaged, escaping  into  the  air  as  carbon  fluoride,  CF4,  while 
the  bath  would  become  poorer  in  aluminium  fluoride.  If  cryo- 
lite alone  were  added  during  the  process,  sodium  fluoride  would 
accumulate  in  the  bath,  and  after  a  certain  time  sodium  would 
be  set  free.  If  the  bath  is  renewed  by  adding  aluminium  fluor- 
ide, this  inconvenience  is  obviated,  but  there  still  remains  the 
question  of  suppressing  the  noxious  fluoride  vapors  set  free.  If 
the  bath  is  renewed  by  placing  alumina  in  the  state  of  fine  pow- 
der in  the  bath,  dropping  it  especially  around  the  anode,  the 
fluorine  set  free  may  reform  aluminium  fluoride  by  attacking 
the  alumina,  setting  free  oxygen,  which  combines  with  the  car- 
bon anode  to  form  carbonic  oxide.  If  the  fluorine  were  not 
completely  absorbed  by  the  alumina,  the  amount  escaping  would 
have  to  be  made  up  for  by  adding  aluminium  fluoride  to  the 
bath.  The  bath  should  therefore  be  fed  by  both  alumina  and 
aluminium  fluoride. 

The  above  contains  Minet's  views  of  what  takes  place  when 
alumina  is  added  to  the  fluoride  bath.  He  does  not  admit  that 
any  alumina  can  be  really  dissolved  in  the  bath  and  be  electro- 


lyzed  as  alumina  (the  view  taken  by  Hall).  Minet,  in  fact, 
maintains  that  when  alumina  is  added  to  molten  cryolite  it 
sinks  through  it  and  remains  undissolved,  as,  for  instance,  very 
fine  marble  dust  would  in  water.  Such,  however,  is  not  the 
experience  of  other  investigators.  According  to  numerous 
experiments  by  Hall  and  others  using  the  present  electrolytic 
processes,  as  well  as  some  made  by  the  writer,  finely-divided 
alumina  appears  to  dissolve  in  molten  cryolite  exactly  as  sugar 
does  in  water,  and  there  is  even  a  saturation  point,  at  about  30 
per  cent.,  above  which  no  more  dissolves.  The  bath  containing 
alumina  forms  to  all  appearances  a  homogeneous  liquid. 
Driven  from  their  first  position,  the  adherents  to  Minet's  views, 
having  allowed  that  a  homogeneous  liquid  bath  does  result,  as- 
sert that  the  alumina  is  only  mechanically  suspended,  like 
clay  in  muddy  water,  and  that  in  this  condition  it  is  carried  to 
the  anode  and  unites  with  the  fluorine  set  free.  Such  a  view, 
however,  is  also  erroneous,  because  regeneration  in  such  a  man- 
ner could  not  be  anything  like  complete,  and  considerable 
amounts  of  fluorine  would  escape ;  yet  in  the  Hall  process, 
when  the  operation  is  properly  conducted,  not  a  trace  of  fluoride 
gas  escapes.  Regeneration  by  mechanically-suspended  alu- 
mina could  not  possibly  be  so  complete. 

We  shall  continue  describing  Minet's  experiments,  asking  that 
it  be  remembered,  however,  that  we  regard  as  erroneous  his 
view  that  aluminium  fluoride  is  the  substance  immediately  de- 
composed by  the  current  when  alumina  is  present. 

Taking  the  bath  already  described,  with  electrodes  of  such 
size  and  distance  apart  that  the  conduction-resistance  at  900° 
was  0.0044  ohms,  the  following  results  were  obtained :  — 


Electromotive  force 


for  decomposition. 

of  the  bath. 


2.4    volts 

.0044  ohms 


2.34     " 

.0033       " 


2.17     " 

.0025       " 

If  V'  =  the  voltage  required  for  decomposition, 
V°  =  the  voltage  required  for  conduction, 
V   =  the  total  voltage  absorbed  by  the  bath, 
A   =;  the  amperage  of  the  current. 

then  [V   =  VI  -(-  AV".] 



We  can  thus  calculate  the  voltage  required  to  send  through 
this  bath  any  number  of  amperes  at  a  given  temperature. 
Thus,  for  lOO  or  looo  amperes  the  voltage  absorbed  per  bath 
would  be  as  follows  : 

Temperature.  Amperes.       Voltage  for 



1 100" 













iltage  for 


Per   cent,  of  total 



voltage  absorbed 
in  conduction  re- 



















It  thus  appears  that,  using  a  bath  of  a  given  size,  the  voltage 
required  to  send  lOOO  amperes  through  it  is  only  2  to  2.5  times 
that  required  for  100  amperes.  Since  the  power  required  is 
just  in  the  same  ratio,  it  follows  that  it  is  economical  to  send  as 
large  a  current  as  practicable  through  a  bath  of  a  given  size. 
The  last  column  shows  us  the  percentage  of  the  energy  of  the 
current  which  will  be  converted  into  heat.  It  follows  from 
these  figures  that  the  heating  effect  of  the  current  increases 
very  rapidly  with  its  quantity,  so  that  a  given  number  of 
amperes  will  supply  enough  heat  to  keep  the  bath  molten  with- 
out exterior  heat;  more  than  this  number  would,  in  fact,  raise 
the  temperature  of  the  bath  too  high,  and  this  limits  the  size  of 
the  current  which  it  is  practicable  to  send  through  a  bath  of  a 
given  size. 

Minet  also  found  that  when  such  a  bath  contained  salts  of 
iron  and  silicon,  which  are  weaker  compounds  than  aluminium 
or  sodium  salts,  a  current  of  carefully  regulated  low  voltage,  and 
consequently  of  low  density,  would  first  separate  these  com- 
pletely. An  experiment  made  with  a  bath  in  which  the  anode 
surface  was  500  square  centimetres,  and  gradually  increasing 
the  voltage,  gave  the  following  successive  results : 


Total        Amperes     Amperes  per      Electro-motive  Nature  of  the 

voltage       passing.       sq.  c.  m.  of      force  of  decom-  metal  deposited. 



position  (volts). 









Iron  ( traces  of  silicon) . 










Ferro-silicon  (traces  of  aluminium) 





Silicon-aluminium  (traces  of  iron) . 





Aluminium  (traces  of  silicon) . 



1. 00 


Aluminium  (traces  of  sodium). 

The  conduction-resistance  of  the  bath  remained  very  nearly 
constant  throughout. 

In  a  large  number  of  experiments,  the  amount  of  metal  actu- 
ally obtained  was  50  to  80  per  cent,  of  the  amount  which 
the  amperage  of  the  current  could  theoretically  produce,  on  an 
average  about  60  per  cent.  As  for  the  power  required,  an 
experiment  lasting  24  hours,  at  a  temperature  of  1 160°,  voltage 
5.75,  and  amperes  1500,  showed  21.5  grammes  of  aluminium 
deposited  per  hour  per  electric  horse-power  used.  Another 
similar  experiment,  but  with  the  electrodes  closer  together,  the 
voltage  consequently  less,  and  at  a  lower  temperature,  gave  31.9 
grammes  per  horse-power-hour,  which  would  be  0.765  kilos 
(1.685  pounds)  per  electric  horse-power  per  day.  As  the  en- 
ergy of  one  horse-power-day  is  equivalent  to  the  energy  of  oxi- 
dation of  2.1  kilos  (4.63  pounds)  of  aluminium,  the  useful  efifect 
over  all  is  36.5  per  cent. 

Quality  of  metal. — When  working  for  pure  aluminium,  about 
three-fourths  of  the  metal  produced  is  taken  from  the  crucible 
in  which  the  cathode  stands,  and  is  98  to  99  per  cent,  pure ; 
the  other  one-fourth  has  been  deposited  on  the  sides  of  the 
cast-iron  pot,  and  contains  10  to  20  per  cent,  of  iron.  It  is 
poured  out  and  used  for  making  ferro-aluminium. 

Installations  of  the  process. — Minet  conducted  his  work  at  the 
expense  of  Messrs.  Bernard  Bros.  The  first  experiments  were 
made  on  the  road  Moulin  Joli,  in  Paris,  from  March,  1887,  to 
March,  1888.  This  plant  consisted  of  a  6  horse-power  engine 
and  a  Gramme  dynamo  capable  of  giving  a  current  of  250 
amperes  at  12  volts  tension.     In  the  year  named,  this  plant  pro- 


duced  about  500  kilogrammes  of  pure  aluminium  and  1500 
kilogrammes  of  ferro-aluminium  or  aluminium  bronze. 

The  second  installation  was  put  up  at  Creil  (Oise),  com- 
menced operations  in  April,  1888,  and  continued  working  until 
October,  1891.  This  plant  had  a  40  horse-power  engine,  and 
an  Edison  dynamo  giving  a  current  of  1200  amperes  and  27.5 
volts.  Regularly  it  was  run  at  only  16  volts,  operating  three 
baths  in  tension,  and  at  looo  amperes.  There  were  made  here 
daily  about  10  kilos  of  pure  aluminium  and  5  to  6  kilos  of  alu- 
minium in  alloys. 

At  the  first  location,  Minet  was  enabled  to  study  experiment- 
ally the  purely  scientific  part  of  his  processes ;  the  plant  at 
Creil  enabled  him  to  solve  the  practical  details  of  the  process. 
In  1889,  the  Messrs.  Bernard  Bros,  determined  to  work  the 
process  on  a  large,  industrial  scale,  and  cast  around  for  a  loca- 
tion having  abundant  water-power.  It  was  decided  to  locate  at 
Saint  Michel  in  Savoy.  The  stream  utihzed  is  the  Valoirette, 
giving  a  volume  of  3.5  cubic  metres  per  second  with  a  fall  of 
133  metres.  This  gives  theoretically  6000  horse-power,  and 
should  produce  4000  electric  horse-power. 

At  this  place  were  put  up  a  turbine  of  300  horse-power  by 
Bouvier  of  Grenoble,  and  a  dynamo  of  275  horse-power  by 
Hillairet-Huguet  of  Paris.  The  latter  gives  a  current  of  4000 
amperes  at  50  volts  tension,  aiid  produces  regularly  about  150 
kilos  (330  pounds)  of  aluminium.  It  is  stated  that  a  600  horse- 
power dynamo,  actuated  by  a  lOOO  horse-power  turbine,  was 
started  during  1894.  Latest  advices  state  that  this  estabUsh- 
ment  has  been  acquired  by  a  French  company  formed  to  work 
under  the  Hall  patents. 

Feldman's  Method   (1887). 

A.  Feldman,  of  Linden,  Hannover,  patented  the  following 
electrolytic  process  :  * — 

A  double  fluoride  of  aluminium  and  an  alkaline  earth  metal, 

*  English  Patent,  No.  12575,  Sept.  16,  1887. 


mixed  with  an  excess  of  a  chloride  of  the  latter  group,  is  either 
electrolyzed  or  reduced  by  sodium.  The  proportions  of  these 
substances  to  be  used  are  such  as  take  place  in  the  following 
reactions : — 

1.  (AUF6+2SrF2)  +  6SrCI.,=2Al+5SrF2+3SrCl2+6Cl. 

2.  (AljF6+2SrF2)+6SrCl2+6Na=2AH-sSrF2+3SrCl2+6NaCl. 

The  three  equivalents  of  strontium  chloride  are  found  in  prac- 
tice to  be  most  suitable.  Potassium  chloride  may  also  be 
added  to  increase  the  fluidity,  but  in  this  case  the  strontium 
chloride  must  be  in  still  greater  excess. 

Even  if  the  above  reactions  and  transpositions  do  take  place, 
the  use  of  so  much  costly  strontium  salts  would  appear  to  ren- 
der the  process  uneconomical. 

Warren's  Experiments  (1887). 

Mr.  H.  Warren,  of  the  Everton  Research  Laboratory,  has 
outlined  the  following  methods  or  suggestions,  some  of  which 
had  already  been  carried  out,  and  probably  others  have  since 
given  useful  ideas  to  workers  in  this  line.  The  principle  can 
hardly  be  called  new,  since  suggestions  almost  identical  with 
Mr.  Warren's  were  made  previously  to  his,  but  the  latter's  re- 
sults are  the  first  recorded  in  this  particular  direction:*  "This 
method  of  preparing  alloys  differs  only  slightly  from  the  man- 
ner in  which  amalgams  of  different  metals  are  prepared,  substi- 
tuting for  mercury  the  metals  iron,  copper,  or  zinc  made  liquid 
by  heat.  These  metals  are  melted,  connected  with  the  negative 
pole  of  a  battery,  and  the  positive  pole  immersed  in  a  bath  of 
molten  salt  floating  on  top  of  the  melted  metal.  The  apparatus 
used  is  a  deep,  conical  crucible,  through  the  bottom  of  which 
is  inserted  a  graphite  rod,  projecting  about  one  inch  within,  the 
part  outside  being  protected  by  an  iron  tube  coated  with  borax. 
As  an  example  of  the  method,  to  prepare  silicon  bronze,  copper 
is  melted  in  the  crucible,  a  bath  of  potassium  silico-fluoride  is 

*  Chemical  News,  Oct.  7,  1887. 


fused  on  top  to  a  depth  of  about  two  inches.  A  thick  platinum 
wire  dips  into  this  salt,  and  on  passing  the  electric  current  an 
instantaneous  action  is  seen,  dense  white  vapors  are  evolved, 
and  all  the  silicon,  as  it  is  produced,  unites  with  the  copper, 
forming  a  brittle  alloy.  Cryolite  may  be  decomposed  in  like 
manner  if  melted  over  zinc,  forming  an  alloy  of  zinc  and  alu- 
minium, from  which  the  zinc  can  be  distilled,  leaving  pure 

Mr.  Warren  does  not  affirm  that  he  has  actually  performed 
the  decomposition  of  cryolite  in  the  way  recommended,  but 
states  that  it  may  be  done ;  from  which  we  would  infer  that  he 
simply  supposed  it  could.  A  well-recorded  experiment,  then, 
is  needed  to  establish  the  truth  of  this  statement.  Neither  does 
he  propose  to  make  aluminium  bronze  in  this  way;  it  may  be 
that  it  was  attempted  and  did  not  succeed,  for  Hampe  states 
that  an  experiment  thus  conducted  did  not  furnish  him  alu- 
minium bronze  (p.  368). 

Zdziarski' s  Patent. 

A.  Zdziarski,*  of  Brest-Litowsk,  Russia,  appears  to  have 
patented  the  above  principle  in  1884,  for  in  his  patent  he  states 
that  the  metal  to  be  alloyed  with  aluminium  is  melted  in  a 
crucible,  covered  with  a  fusible  compound  of  aluminium  for  a 
flux  (alumina  and  potassium  carbonate  may  be  used)  and  made 
the  negative  pole  of  an  electric  current,  the  positive  pole  being 
a  carbon  rod  dipping  in  the  flux. 

Grabau's  Apparatus. 

LudwigGrabaUjf  of  Hannover,  Germany,  proposes  to  electro- 
lyze  a  molten  bath  of  cryolite  mixed  with  sodium  chloride.  The 
features  of  the  apparatus  used  are  an  iron  pot,  in  which  the 
bath  is  melted,  and  water-cooled  cylinders  surrounding  both 
electrodes,  the  jacket  surrounding  the  negative  one  having  a 

*  English  Patent  3090,  Feb.  11,  1884. 
t  German  Patent  (D.  R.  P.),  No.  45012. 


bottom,  the  other  not.  The  object  of  these  cylinders  is,  at  the 
positive  electrode,  to  keep  the  liberated  fluorine  from  attacking 
the  iron  pot  and  so  contaminating  the  bath,  at  the  other  pole 
the  liberated  aluminium  is  kept  from  dropping  to  the  bottom 
of  the  pot,  where  it  might  take  up  iron,  and  can  be  removed 
from  the  bath  by  simply  lifting  out  the  water-cooled  cylinders 
and  carbon  electrode.  Mr.  Grabau  states  that  he  has  abandoned 
this  process  because  the  inseparable  impurities  in  the  cryolite 
produced  impurities  in  the  metal;  it  may  be  that  with  the  pure 
artificial  cryolite,  which  he  makes  by  his  other  processes  (see 
p.  171),  this  electrolytic  process  may  again  be  taken  up.  (See 
also  p.  294.) 

Rogers'  Process  (1887). 

In  July,  1887,  the  American  Aluminium  Company,  of  Mil- 
waukee, was  incorporated,  with  a  capital  stock  of  $1,000,000, 
for  the  purpose  of  extracting  aluminium  by  methods  devised 
by  Prof.  A.  J.  Rogers,  a  professor  of  chemistry  in  that  city. 
This  gentleman  had  been  working  at  the  subject  for  three  or 
four  years  previous  to  that  time,  but  it  has  not  been  until  re- 
cently that  patents  have  been  applied  for,  and  they  are  still 

The  principle  made  use  of  has  already  been  suggested  in  con- 
nection with  the  production  of  sodium  (p.  219).  It  is  briefly, 
that  if  molten  sodium  chloride  is  electrolyzed,  using  a  molten 
lead  cathode,  a  lead-sodium  alloy  is  produced.  This  alloy  is 
capable  of  reacting  on  molten  cryolite,  setting  free  aluminium, 
which  does  not  combine  with  the  lead  remaining  because  of  its 
weak  affinity  for  that  metal.  If,  then,  cryolite  is  placed  in  the 
bath  with  the  sodium  chloride,  the  two  reactions  take  place  at 
once,  and  aluminium  is  produced.  In  the  early  part  of  1888, 
the  company  erected  a  small  experimental  plant,  with  a  ten- 
horse-power  engine,  with  which  the  following  experiments, 
among  many  others,  were  made:  — 

I.  *A  current  of  60  to  80  amperes  was  passed  for  several 

*  Proceedings  of  the  Wisconsin  Nat.  His.  Soc,  April,  1889. 


hours  through  a  bath  of  cryolite  melted  in  a  crucible  lined  with 
alumina,  and  using  carbon  rods  2^  inches  in  diameter  as 
electrodes,  one  dipping  into  the  bath  from  above,  the  other 
passing  through  the  bottom  of  the  crucible  into  the  bath. 
Only  I  or  2  grammes  of  aluminium  were  obtained,  showing 
that  the  separated  metal  was  almost  all  redissolved  or  reunited 
with  fluorine.  With  the  temperature  very  high,  it  was  found 
that  sodium  passed  away  from  the  bath  without  reducing  the 

2.  A  current  averaging  54  amperes  and  10  volts  was  passed 
for  five  and  a  half  hours  through  a  mixture  of  I  part  cryolite 
and  5  parts  sodium  chloride  placed  in  a  crucible  with  3 70 
grammes  of  molten  lead  in  the  bottom  as  the  cathode.  After 
the  experiment,  25  grammes  of  aluminium  were  found  in 
globules  on  top  of  the  lead-sodium  alloy.  This  latter  alloy 
contained  some  aluminium.  The  globules  were  about  as  pure 
as  ordinary  commercial  aluminium,  and  contained  no  lead  or 
sodium.  From  another  experiment  it  was  determined  that  the 
lead-sodium  alloy  must  first  acquire  a  certain  richness  in 
sodium  before  it  will  part  with  any  of  that  metal  to  perform 
the  reduction  of  the  cryolite.  It  was  also  found  that  a  certain 
temperature  was  necessary  in  order  that  aluminium  be  pro- 
diiced  at  all. 

3.  A  current  of  75  amperes  and  about  5  volts  suflficed  to  de- 
compose the  bath  and  to  produce  105  grammes  of  aluminium 
in  seven  hours.  This  would  be  nearly  30  grammes  per  hour 
for  each  electric  horse-power. 

4.  A  current  of  80  amperes  and  24  volts  was  passed  through 
four  crucibles  connected  in  series  for  six  hours,  using  a  bath 
of  I  part  cryolite  and  3  parts  sodium  chloride  with  450 
grammes  of  lead  in  each  crucible.  The  crucibles  were  heated 
regularly  to  a  moderate  temperature.  There  were  obtained 
altogether  250  grammes  of  quite  pure  aluminium.  This  would 
be  equal  to  16  grammes  per  electric  horse-power-hour. 

"  A  large  number  of  similar  experiments  afforded  a  return  of 
^  to  I  ^  lbs.  of  aluminium  per  electric  horse-power  per  day. 


The  experimental  plant  now  in  operation  consists  of  a  40  volt 
— TOO  ampere — dynamo,  the  current  being  sent  through  six  pots 
connected  in  series.  When  the  bath  is  completely  electrolyzed 
the  contents  of  the  crucible  are  tapped  ofif  at  the  bottom  and  a 
fresh  supply  of  melted  salt  poured  in  quickly.  The  lead- 
sodium  alloy  run  off  is  put  back  into  the  crucibles,  thus  keep- 
ing approximately  constant  in  composition  and  going  the 
rounds  continuously.  With  this  apparatus,  3  to  4  lbs.  of  alu- 
minium are  produced  regularly  per  day  of  12  hours.  As  soon 
as  patents  are  obtained,  it  is  the  intention  of  the  company  to 
put  up  a  plant  of  50  lbs.  daily  capacity,  which  can  be  easily 
increased  to  any  extent  desired  as  the  business  expands." 

Professor  Rogers  observes  in  regard  to  the  apparatus  that  he 
has  tried  various  basic  linings  for  his  clay  crucibles,  but  a  paste 
of  hydrated  alumina,  well  fired,  has  succeeded  best.  Some 
"shrunk"  magnesia  lining,  such  as  is  used  in  basic  steel  fur- 
naces, answered  well,  but  could  not  be  used  because  of  the 
amount  of  iron  in  it.  Lime  could  not  be  used,  as  it  fluxed 
readily.  The  carbon  rods  lasted  48  hours  without  much  cor- 
rosion if  protected  from  the  air  during  electrolysis.  Carbon 
plates  and  cylinders  were  tried,  but  the  solid  rods  gave  the 
best  results.  About  8  to  10  per  cent,  of  aluminium  can  be 
extracted  from  cryolite  containing  12.85  P^r  cent.  The  min- 
eral used  was  obtained  from  the  Pennsylvania  Salt  Company, 
and  was  called  pure,  but  it  contained  2  per  cent,  of  silica  and 
I  per  cent,  of  iron.  These  impurities  pass  largely  into  the 
aluminium  produced,  but  the  company  hoped  to  be  able  to 
manufacture  an  artificial  aluminium  fluoride  which  will  not 
only  be  purer  but  less  costly  than  this  commercial  cryolite. 
Professor  Rogers  infers  that  pure  aluminium  fluoride  would  not 
be  an  electrolyte,  since  the  resistance  of  the  bath  increases  as 
the  amount  of  other  salts  present  decreases. 

It  is  useless  to  base  any  accurate  estimation  of  the  cost  of 
aluminium  by  this  process  on  the  data  given  above,  since  they 
were  only  for  a  small  experimental  plant.  If,  however,  75  per 
cent,  of  the  aluminium  in  cryolite  can  be  extracted  at  the  rate 


of  I  lb.  of  metal  per  day  per  electric  horse-power,  and  the 
metal  is  free  from  lead  and  sodium,  (a  sample  sent  me  was 
of  very  fair  quality,)  it  would  seem  that  the  process  was  in  a 
fair  way  to  compete  on  an  equal  footing  with  the  other  electro- 
lytic processes  as  operated  in  1889,  but  it  has  been  entirely 
distanced  by  more  recent  developments. 

Dr.  Hampe  on  the  Electrolysis  of  Cryolite. 

Prof.  W.  Hampe,  of  Clausthal,  whose  name  is  a  guarantee  of 
careful  and  exact  observations,  has  written  the  following  val- 
uable information  on  this  subject,  in  presenting  which  we  will 
also  give  the  remarks  of  Dr.  O.  Schmidt,  called  forth  by 
Hampe's  first  article. 

*"  The  electrolysis  of  a  bath  of  cryolite  mixed  with  sodium 
and  potassium  chlorides,  using  a  layer  of  melted  copper  in  the 
bottom  of  the  crucible  as  cathode  and  a  carbon  rod  as  anode, 
gave  balls  of  melted  sodium  which  floated  on  the  surface  and 
burnt,  but  scarcely  a  trace  of  aluminium.  Yet  here  the  condi- 
tions were  most  favorable  to  the  production  of  the  bronze.  The 
battery  used  consisted  of  twelve  large  zinc-iron  elements.'' 

fDr.  O.  Schmidt,  referring  to  this  statement  of  Hampe's, 
quotes  an  opposite  experience.  He  fused  cryolite  and  sodium 
chloride  together  in  a  well-brasqued  crucible  in  the  proportions 
indicated  by  the  reaction 

AUF6.6NaF+6NaCl=Al2Cle+i  2NaF. 

At  a  clear  red  heat  the  bath  becomes  perfectly  fluid  and  trans- 
parent, and  an  anode  of  gas  carbon  and  a  cathode  of  sheet  cop- 
per are  introduced.  On  passing  the  current  the  copper  did  not 
melt  but  became  covered  with  a  film  of  deposited  aluminium, 
which  in  part  penetrated  the  electrode  and  in  part  adhered  to 
the  surface  as  a  rich  alloy  which  ultimately  fused  ofif  and  sank 
to  the  bottom  of  the  crucible.  With  a  plate  i  to  i  ^  millimetres 
thick,  10  per  cent  of  its  weight  of  aluminium  could  thus  be  de- 

*  Ghemiker  Zeitung,  xii.,  391  (1888).  fldem,  xii.,  457  (i 


posited ;  with  one  3  millimetres  thick,  about  5  per  cent.  The 
metal  could  be  made  perfectly  homogeneous  by  subsequent 
fusion  in  a  graphite  crucible.  Dr.  Schmidt  further  remarks 
(evidently  on  the  supposition  that  the  reaction  he  gives  actually 
takes  place)  that  on  thermo-chemical  grounds  sodium  would  not 
here  be  reduced,  because  while  the  molecule  of  sodium  chloride 
requires  97.3  calories  for  its  decomposition,  that  of  aluminium 

chloride,  — ^,  requires  only  80.4,  and  the  current  would  attack 

first  the  most  easily  decomposed.  He  also  states  that  the  cal- 
culated difference  of  potential  for  the  dissociation  of  aluminium 
chloride  which  is  ^'^  =  3.5  volts,  was  actually  observed,  and  the 

tension  of  the  current  must  have  been  increased  to  about  4.5 
volts  to  bring  about  the  decomposition  of  the  sodium  chloride.* 

Dr.  Hampe's  statement  occasioned  several  other  communica- 
tions, which  he  considers  and  replies  to  in  the  following 
article :  f — 

"  Dr.  O (whose  name  I  withhold  at  his   own   request) 

writes  to  me  that  by  electrolyzing  pure  cryolite,  using  a  nega- 
ative  pole  of  molten  copper,  he  never  obtained  aluminium 
bronze ;  but,  on  the  other  hand,  always  obtained  it  if  he  used 
the  mixture  of  cryolite  and  sodium  chloride  mentioned  by  Dr. 
Schmidt,  and  in  place  of  the  molten  copper  a  thick  stick  of  the 
unfused  metal.  A  letter  from  R.  Gratzel,  Hannover,  contains  a 
similar  confirmation  of  the  latter  observation.  By  electrolyzing 
a  mixture  of  100  parts  cryolite  with  150  of  sodium  chloride  in 

*  Aside  from   Hampe's  subsequent  remarks  as  to  no  aluminium  chloride  being 
formed,  we  would  further  point  out  the  fact  that  the  decomposition  of  a  chemically 

equivalent  quantity  of  aluminium   chloride  requires  not   — ^  =  80.4  calories,  but 

^"'  °°  or  53.6  calories,  and  the  calculated  difference  of  potential  is  properly -^^ 

or  2.3  volts.  The  fact  that  the  observed  tension  was  3.5  volts  shows  that  the  current 
was  not  strong  enough  to  decompose  the  sodium  chloride,  as  Schmidt  observes,  and 
the  fact  that  this  current  deposited  aluminium  would  show  that  the  heat  of  formation 
of  aluminium  fluoride  at  this  temperature  cannot  be  greater  than  23X3.5X6^483 
(thousand)  calories. 
tChemiker  Zeitung  (Cothen),  xiii.,  29  and  49. 


a  graphite  crucible  holding  30  kilogrammes,  aluminium  bronze 
dripped  down  from  the  ring-shaped  copper  cathode  used,  while 
chlorine  was  freely  disengaged  at  the  carbon  anode.  But  after 
a  time,  long  before  the  complete  decomposition  of  the  cryolite, 
the  formation  of  bronze  stopped — even  an  attacking  of  that 
already  formed  sometimes  taking  place.  Pellets  of  an  alloy 
of  sodium  and  aluminium  appear  on  the  surface  and  burn  with 
a  white  light. 

"  These  comments  excited  me  to  further  research  in  the  mat- 
ter. At  first,  it  was  necessary  to  consider  or  prove  whether  by 
melting  sodium  chloride  with  cryolite  a  true  chemical  decom- 
position took  place,  such  as  Dr.  Schmidt  supposed.  If  this 
were  the  case,  the  very  volatile  aluminium  chloride  must  neces- 
sarily be  mostly  driven  off  on  melting  the  mixture,  and  at  a 
temperature  of  700°  to  1000°  C.  there  could  not  be  any  left  in 
it.  But  an  experiment  in  a  platinum  retort  showed  that  such  a 
reaction  positively  does  not  occur ;  for  neither  was  any  alu- 
minium chloride  volatilized,  nor  did  the  residue  contain  any, 
for  on  treatment  with  water,  it  gave  up  no  trace  of  a  soluble 
aluminium  compound.  During  the  melting  of  the  mixture,  acid 
vapors  proceeded  from  the  retort,  and  a  small  quantity  of  cryo- 
lite was  volatilized  into  the  neck  of  the  retort.  Dr.  Klochman 
has  shown  that  cryolite  always  contains  quartz,  even  colorless, 
transparent  pieces,  which  to  the  naked  eye  appear  perfectly 
homogeneous,  showing  it  when  examined  in  thin  sections  under 
the  microscope,  and  on  melting  the  mineral  opportunity  is 
given  for  the  following  reactions  : 

SiOa  4-  4NaF  =  SiF,  +  2Na20, 
sNa^O  +  Al^Fe  =  6NaF  +  AUO,, 

as  is  rendered  probable  by  the  appearance  of  delicate  crystals 
of  alumina  on  the  inner  surface  of  the  retort  just  above  the 
fusion.  The  silicon  fluoride  probably  passes  away  as  silico- 
fluoride  of  sodium. 

"  If  cryolite  is  fused  with  such  metallic  chlorides  that  really  do 


bring  about  a  decomposition,  there  is  never  any  aluminium 
chloride  formed  in  these  cases,  but  the  sodium  of  the  cryolite  is 

exchanged  for  the  other  metal.     Dr.  O ,  to  whom  I  owe  this 

observation,  fused  cryolite  with  calcium  chloride,  hoping  that 
aluminium  chloride  would  distil,  but  obtained  instead  crystals 
of  the  calcium  salt  of  alumina-fluoric  acid ;  thus, 

NaeAljFi,  +  aCaClj  =  6NaCl  +  CajAl^Fi^, 

and  in  like  manner  can  be  obtained  the  analogous  strontium  or 
barium  compounds. 

"  Just  as  erroneous  as  the  supposed  production  of  aluminium 
chloride  are  the  other  arguments  advanced  by  Dr.  Schmidt,  re- 
garding the  reasons  why  sodium  could  not  be  set  free.  The 
self-evident  premises  for  the  propositions  are  lacking,  viz. :  that 
the  two  bodies  compared  are  conductors.  On  the  contrary,  I 
have  previously  shown*  that  aluminium  chloride  and  bromide, 
and  more  certainly  its  fluoride,  belong  to  the  non-conductors. 
It  follows,  then,  that  there  can  remain  no  doubt  that  on  elec- 
trolyzing  pure  cryolite,  or  a  mixture  of  it,  with  sodium  chloride, 
only  sodium  will  be  set  free  at  first,  either  from  sodium  fluoride 
or  the  more  easily  decomposable  sodium  chloride.  The  pres- 
ence or  absence  of  sodium  chloride  is  consequently,  chemically, 
without  significance. 

"  Since  the  experiments  with  solid  cathodes  gave  aluminium, 
while  those  with  molten  copper  did  not,  these  results  being 
independent  of  the  presence  or  absence  of  sodium  chloride,  the 
next  attempt  made  was  to  seek  for  the  cause  of  the  different  re- 
sults in  the  differences  of  temperature.  It  was  found  that  when 
the  electrolysis  takes  place  at  a  temperature  about  the  melting 
point  of  copper,  bubbles  of  sodium  vapor  rise  and  burn,  and  any 
aluminium  set  free  is  so  finely  divided  that  it  is  attacked  and 
dissolved  by  the  cryolite.  To  explain  this  action  of  the  cryo- 
lite it  is  necessary  to  admit  the  formation  of  a  lower  fluoride  of 
aluminium  and  sodium,  such  as  I  have  recently  proven  the  exist- 

*  Chemiker  Zeitung  (Cothen),  xi.,  p.  934  (1887). 


ence  of.*  The  solution  of  the  aluminium  takes  place  according 
to  the  following  reaction: 

Al^Fe.eNaF  +  Al  =  3  (AlF2.2NaF) . 

If  the  electrolysis  takes  place  at  a  temperature  so  low  that  the 
sodium  separates  out  as  a  liquid  (its  volatilizing  point  is  about 
900°),  large  globules  of  aluminium  will  be  produced,  on  which 
the  cryolite  seems  to  exert  no  appreciable  action.  Nevertheless, 
the  yield  of  aluminium  is  much  below  the  theoretical  quantity 
set  free.  Since  pure  copper  melts  at  1050°,  and  aluminium 
bronze  at  800°,  the  copper  electrodes  can  remain  unfused  in  the 
bath  while  the  bronze  melts  off  as  it  forms,  while  the  tempera- 
ture can  be  low  enough  to  keep  the  sodium  in  the  liquid  state. 
By  mixing  sodium  or  potassium  chlorides  with  the  cryolite,  the 
melting  point  is  lowered,  or  at  a  given  temperature  the  bath  is 
more  fluid,  and  so  easier  to  work.  When  there  is  not  enough 
aluminium  fluoride  present  in  the  bath  to  utilize  all  the  sodium 
liberated,  the  excess  of  sodium  may  form  an  alloy  with  some 
aluminium,  and  rising  to  the  surface,  burn  to  waste.  Since  cry- 
olite always  contains  silica,  as  previously  explained,  the  bronze 
thus  obtained  is  always  rendered  hard  with  silicon,  and  is  not  of 
much  value  commercially.'' 

Hall's  Process. 
Although  Hall's  patents  were  not  issued  by  the  patent  office 
until  1889,  yet  they  were  applied  for  in  the  middle  of  1886,  and 
a  commercial-sized  plant  was  put  up  to  work  the  process  in 
1888.  Mr.  Hall  really  discovered  the  principle  on  which  his 
process  is  based,  and  made  some  aluminium  by  it,  on  a  small 
scale,  in  February,  1886. 

*Chem.  Zeit.  (Cothen),  xiii.,  p.  I  (1879).  Hampe  melted  together  aluminium  and 
sodium  fluorides  in  the  proportions  of  one  molecule  of  the  first  to  four  of  the  second, 
and  obtained  what  is  apparently  a  lower  fluoride  than  cryolite,  in  which  aluminium 
cannot  be  otherwise  than  diatomic,  since  analysis  gives  it  the  formula  AlF2.2NaF. 
This  salt  is  similar  in  appearance  and  properties  to  cryolite.  As  there  are  still  some 
doubts,  however,  about  this  compound,  the  above  explanation  of  the  solution  of  alu- 
minium by  the  cryolite  need  not  be  accepted  as  final. 


The  inventor  of  this  process,  Charles  M.  Hall,  of  Oberlin, 
Ohio,  born  in  1863,  is  a  graduate  of  Oberlin  College,  and  while 
yet  a  student  spent  considerable  time  in  experimenting  on  iso- 
lating aluminium  with  the  electric  current.  Less  than  a  year 
after  leaving  college,  he  conceived  the  following  idea,  which  I 
quote  in  his  own  words :  "  It  occurred  to  me  that  if  I  could  find 
some  stable  solvent  for  alumina  itself,  which  at  a  reasonable 
and  practicable  temperature  would  dissolve  the  alumina  by  the 
mere  mingling  of  it  with  the  solvent  and  allow  the  alumina  so 
dissolved  to  be  electrolyzed  out  of  it,  leaving  the  solvent  unaf- 
fected, this  would  possibly  be  the  best  process  which  could  be 
devised  for  the  manufacture  of  aluminium  by  electrolysis." 
Many  different  salts  were  tried,  to  see  if  they  possessed  the 
property  required,  among  them  the  fluorides  of  calcium,  mag- 
nesium, sodium  and  potassium.  These  latter  salts  were  the 
only  ones  which  gave  any  encouraging  results,  but  the  first  two 
were  too  hard  to  fuse,  and  they  all  dissolved  only  small  quan- 
tities of  alumina.  Hall  next  tried  cryolite,  the  natural  com- 
pound of  aluminium  and  sodium  fluorides,  and  found  that  it 
melted  at  a  red  heat  and  readily  dissolved  considerable  alumina. 
This  was  on  February  10,  1886.  On  applying  the  electric  cur- 
rent to  this  bath  he  was  not  immediately  successful ;  but,  at- 
tributing the  failure  to  the  presence  of  silica  in  the  crucible 
lining,  he  tried  a  crucible  with  a  carbon  lining,  and  the  experi- 
ment was  entirely  successful.  This  was  February  23,  1886,  and 
on  July  9,  of  the  same  year.  Hall  applied  for  patents  covering 
his  invention. 

P.  L.  V.  Heroult,  of  Paris,  France,  had,  however,  apphed  for 
a  United  States  patent  for  substantially  the  same  process  on 
May  22,  1886,  and  the  patent  ofifice  declared  an  interference 
and  ordered  both  parties  to  give  evidence  as  to  the  date  of 
invention  and  putting  into  practice.  Hall  was  able  to  name 
February  23,  1886,  as  the  date  on  which  he  had  put  his  inven- 
tion into  practical  operation,  while  Heroult  named  only  the 
date  of  his  French  patent  for  the  same  invention,  April  23, 
1886.     (See  p.  386.)     The  result  of  these  proceedings  was 


that  a  patent  covering  the  process  was  issued  to  Hall  on  April 
2,  1889.  (Number  400,766.)  This  patent  has  claims  cover- 
ing the  use  of  the  following  process : 

1.  Dissolving  alumina  in  a  fused  bath  composed  of  the 
fluorides  of  aluminium  and  a  metal  more  electropositive  than 
aluminium,  and  then  passing  an  electric  current  through  the 
fused  mass. 

2.  Dissolving  alumina  in  a  fused  bath  composed  of  the 
fluorides  of  aluminium  and  sodium,  and  then  passing  an 
electric  current,  by  means  of  a  carbonaceous  anode,  through 
the  fused  mass. 

In  the  specification  of  the  patent,  it  is  stated  that  the  bath 
preferred  as  a  solvent  contains : 

Sodium  fluoride 33.2  per  cent. 

Aluminium  fluoride 66.8  per  cent. 

represented  by  the  formula  AlFj.NaF.  A  convenient  method 
of  forming  this  bath  consists  in  adding  to  the  mineral  cryolite 
80.3  per  cent,  of  its  weight  of  aluminium  fluoride,  according  to 
the  formula : 

AlFs.sNaF  +  2AIF3  =  sCAlFs.NaF). 

It  is  further  stated  that  the  bath  may  be  fused  in  a  crucible 
or  melting  pot  of  iron  or  steel  having  a  carbon  lining,  that  the 
positive  electrode  may  be  of  carbon,  copper,  platinum  or  any 
other  suitable  material,  and  the  negative  electrode  a  carbon 
rod  or  the  carbon  lining  of  the  bath.  When  the  positive 
electrode  is  carbon  it  is  gradually  consumed  by  the  oxygen 
liberated,  but  when  copper  is  used  a  coating  of  copper  oxide 
is  at  once  formed  on  it,  which  protects  it  from  further  oxidation 
and  causes  free  oxygen  to  be  liberated.  The  tension  required 
to  operate  a  bath  is  stated  as  4  to  6  volts. 

The  above  description  may  be  taken  as  summarizing  Hall's 
process  as  developed  by  him  at  the  date  of  application  for  his 
patent,  July,  1886.  It  is  the  writer's  opinion  that  credit  should 
be  given  to  both  Hall  and  Heroult  for  originating  this  inven- 


tion,  as  the  principle  was  discovered  independently  by  each  at 
very  nearly  the  same  time ;  but  in  the  subsequent  development 
and  practical  application  of  the  invention,  Hall  in  America 
clearly  outstripped  Heroult  in  Europe. 

Several  other  patents  were  subsequently  applied  for  by  Hall, 
covering  modifications  of  the  original  process,  and  these  were 
all  issued  with  the  original  patent  in  1889.*  One  covers  the 
use  of  a  potassium-aluminium  fluoride,  AIF3.KF,  instead  of  the 
corresponding  sodium  salt,  since  it  is  much  more  fusible. 
Also  the  addition  of  lithium  fluoride  to  this  salt.  Another 
covers  the  use  of  calcium  and  aluminium  fluorides  to  form  the 
bath,  such  as  2AlF3.CaF2  or  2AlF3.3CaF2.  Since  this  bath  is  of 
higher  specific  gravity  than  molten  aluminium,  it  is  recom- 
mended to  add  to  it  enough  of  the  salt  AIF3.KF  to  lower  the 
specific  gravity  below  that  of  the  aluminium.  This  is  unneces- 
sary if  alloys  of  aluminium  are  to  be  made,  in  which  case  the 
metal  to  be  alloyed  is  made  the  negative  electrode  and  the 
alloy  formed  will  be  sufficiently  heavy  to  sink.  For  making 
alloys,  the  addition  of  barium  fluoride  to  the  bath  is  recom- 
mended, as  its  high  specific  gravity  is  no  inconvenience  and  it 
is  more  fusible  than  the  calcium  or  strontium  fluorides.  In 
another  of  these  patents,  the  bath  specified  has  the  formula 
2(AlF3.3NaF)  +  aAlFj-CaFj,  being  made  by  melting  together 
cryolite,  aluminium  fluoride  and  fluorspar.  When  the  bath 
becomes  clogged,  by  the  settling  out  of  a  mushy  deposit  which 
stops  the  current,  the  addition  of  3  or  4  per  cent,  of  anhydrous 
calcium  chloride  is  recommended  as  clearing  or  liquefying  the 
bath ;  this  addition  is  also  said  to  lessen  the  disintegration  of 
the  carbon  anodes  used. 

As  at  present  conducted,  the  process  is  worked  according  to 
the  original  patent  applied  for  in  1886,  it  having  been  found 
that  almost  all  the  difficulties  which  the  subsequent  modifica- 
tions were  designed  to  overcome  are  entirely  obviated  by  regu- 
lar working  on   a  large  scale.     It  has  been  concluded   from 

*  Numbers  400,664;   400,665;   400,666;   400,667;   400,766. 


subsequent  experience  that  almost  all  the  difficulties  met  at 
first  were  the  results  of  the  varying  composition  of  the  bath 
and  its  irregular  temperature,  and  were  inherent  in  attempts  to 
work  on  a  small  scale. 

From  June,  1887,  to  the  middle  of  1888,  Mr.  Hall  experi- 
mented on  his  process  at  the  Cowles'  Bros,  works  at  Lockport, 
N.  Y.  His  results  here,  working  on  a  small  scale,  were  not 
sufficiently  economical  to  induce  that  company  to  continue  the 
work.  Mr.  Hall,  however,  was  confident  that  if  the  process 
could  be  started  on  a  large  scale,  aluminium  could  be  made  at 
a  cost  very  much  below  its  selling  price  at  that  time.  Leaving 
Lockport,  Mr.  Hall  went  to  Pittsburgh,  and  there,  through  the 
influence  of  Mr.  Romaine  C.  Cole,  was  successful  in  interesting 
several  capitalists,  who  contributed  $20,000  in  cash  to  put  up  a 
works,  and  in  September,  1888,  organized  the  Pittsburgh  Reduc- 
tion Company,  with  a  capital  stock  of  $1,000,000.  The  con- 
struction of  the  plant  was  immediately  begun,  and  in  Novem- 
ber, 1888,  aluminium  was  being  produced  at  the  rate  of  50 
pounds  per  day,  which  found  a  ready  sale  at  $5  per  pound, 
leaving  a  handsome  profit. 

This  plant  was  situated  in  Pittsburgh,  and  was  operated  by 
steam-power,  using  coal  for  fuel.  The  machinery  consisted  of 
two  ordinary  tubular  boilers  of  sixty  horse-power  each,  and  a 
Westinghouse  "  automatic  "  engine  of  125  horse-power,  running 
two  shunt-wound  Westinghouse  dynamos.  These  dynamos, 
running  at  1,000  revolutions,  gave  each  a  current  of  1,000 
amperes  at  25  volts  tension,  and  being  coupled  in  parallel  gave 
a  current  of  2,000  amperes  at  full  speed,  or  an  average  of  1,700 
to  1,800  amperes  at  16  volts  on  steady  runs.  This  current  was 
passed  through  two  reducing  pots,  coupled  in  series.  These 
pots  were  of  cast-iron,  24  inches  long,  16  inches  wide  and  20 
inches  deep,  lined  inside  with  a  layer  of  hard-baked  carbon  3 
inches  thick.  From  a  copper  bar  above  were  suspended,  by 
^  inch  copper  rods,  6  to  10  three-inch  carbon  cylinders,  each 
originally  15  inches  long.  Each  pot.  held  200  to  300  pounds 
of  the  electrolyte. 


It  was  found  that  with  apparatus  and  current  of  this  size, 
outside  heating  was  not  necessary;  the  heat  generated  by  the 
passage  of  the  current  being  sufficient  to  keep  the  bath  fused 
at  the  proper  temperature.  Larger  pots  have  since  been  used, 
which  will  be  described  later,  but  as  the  operation  in  them  is 
exactly  similar  to  that  in  the  smaller  ones,  we  will  describe  the 
process  at  once. 

The  carbon  lining  of  the  pot  forms  the  negative  electrode, 
connection  being  made  to  the  iron  casing.  The  fluoride  salts 
to  form  the  bath  are  placed  in  the  bottom  of  the  cavity,  the 
carbon  positive  electrodes  lowered  until  they  touch  the  carbon 
lining,  and  the  current  turned  on.  After  a  few  minutes  the 
salt  is  melted  and  when  red-hot  in  the  vicinity  of  each  carbon, 
more  salt  is  thrown  around  the  carbons,  or  each  carbon  moved 
up  a  little.  In  an  hour  or  two  sufficient  salt  has  been  melted  to 
form  the  bath,  and  the  carbons  have  been  brought  out  of  direct 
contact  with  the  lining.  The  bath  is  now  ready  to  dissolve 
alumina,  which  is  first  sprinkled  on  top  of  the  bath,  and  after 
it  has  become  hot  and  perfectly  dry  is  stirred  in. 

The  fumes  which  were  arising  from  the  decomposition  of  the 
fluorine  salts  immediately  cease,  the  voltage  absorbed  by  the 
bath  falls,  the  number  of  amperes  passing  increases,  and  the 
electrolysis  of  the  dissolved  alumina  commences  at  once. 
Powdered  carbon  (the  stub  ends  of  electrodes  ground  up)  is 
now  placed  on  top  of  the  bath  in  a  layer  about  an  inch  thick, 
serving  to  keep  in  the  heat  and  so  reduce  the  loss  by  radiation. 
The  carbon  electrodes  are  clamped  to  a  copper  bar  extending 
the  whole  length  of  the  pot  (see  Fig.  38),  and  if  one  part  of 
the  bath  becomes  cooler  than  it  should  be,  the  carbons  are 
crowded  together  at  that  point  and  soon  heat  it  up.  In  prac- 
tice, the  ends  of  the  carbons  are  kept  about  0.5  to  i  inch  from 
the  lining,  and  each  one  carries  about  250  to  300  amperes.  If 
more  current  than  this  passes  through  a  carbon,  as  might  happen 
if  it  short-circuited,  the  copper  rod  becomes  red-hot  at  its  con- 
nection with  the  carbon.  As  soon  as  this  is  observed,  the 
workman  raises  it  slightly  and  so  stops  the  extra  current.     The 



carbons  wear  down  gradually  until  only  3  or  4  inches  long  (the 
depth  of  liquid  bath  is  not  over  6  inches)  and  must  then  be 
replaced.  The  consumption  of  carbons  in  regular  running  is 
less  than  one  pound  per  pound  of  aluminium  produced,  show- 
ing that  they  are  burnt  according  to  the  reaction 

AI.O,  +  3C  =  2AI  +  3CO. 

in  which  102  parts  of  alumina  would  require  36  parts  of  car- 
bon to  combine  with  its  oxygen,  producing  54  parts  of  metal. 

Fig.  38. 

Theoretically,  therefore,  there  is  required  ||  or  ^  of  a  pound 
of  carbon  to  i  pound  of  aluminium  produced.  The  smal'l 
amount  over  this  actually  used  is  consumed  by  the  air  with 
which  they  inevitably  come  in  contact. 

In  these  small  pots,  a  tension  of  8  volts  is  required  to  oper- 
ate each,  at  an  amperage  of  1800.  If  the  voltage  rises  to  10 
or  more,  it  indicates  that  the  alumina  in  the  bath  has  become 
exhausted,  as  is  also  shown  by  dense,  irritating  fluoride  fumes. 


The  workman  at  once  stirs  in  some  of  the  alumina  which  is 
always  kept  on  top  of  the  carbon  covering,  and  the  voltage 
immediately  falls.  A  delicate  electrical  instrument,  set  to  a 
certain  voltage,  gives  immediate  notice  to  the  workman  when 
the  bath  is  "  out  of  ore."  In  regular  working  no  fumes  arise, 
the  carbon  covering  entirely  conceals  the  red-hot  fluid  bath 
beneath,  and  one  can  only  convince  himself  that  the  bath  is 
really  in  operation  by  approaching  and  noticing  the  heat 
radiated.  When  aluminium  has  accumulated  for  several  hours, 
it  is  ladled  out  with  iron  ladles  well-rubbed  with  chalk  or 
plumbago.  This  operation  gives  rise  to  some  fumes,  and  also 
causes  some  of  the  electrolyte  to  be  dipped  out  with  the  metal. 
It  has  been  suggested  that  a  tap-hole  should  be  provided,  but 
there  was  found  great  difficulty  in  keeping  the  pot  tight  when 
this  was  tried,  and  the  expedient  of  syphoning  out  the  metal 
has  been  found  more  practicable. 

The  crude  ingots  thus  poured  are  re-melted  in  large  crucibles ; 
the  re-melting  plant  is  shown  in  Fig.  39. 

The  alumina  used  in  this  plant  was  from  the  German  manu- 
turer,  Bergius,  at  Goldschmeiden,  near  Breslau,  Silesia.  As  im- 
ported, it  contained  about  33  per  cent,  of  moisture,  which  is 
driven  off  in  a  drying  furnace.  The  cost  of  alumina  was,  in 
1890,  five  cents  a  pound  delivered  in  Pittsburgh,  which  would 
make  the  dried  alumina  cost  7.5  cents  per  pound  plus  the  cost 
of  calcining,  which  is  not  over  0.5  cent.  If  absolutely  pure, 
alumina  should  contain  52.94  per  cent,  of  aluminium,  but  as 
this  calcined  alumina  usually  contains  about  i  per  cent,  of  im- 
purities, chiefly  silica,  there  is  only  a  little  over  52  per  cent,  of 
metal  in  it.  An  accurate  account  of  several  months'  running 
showed  that  the  Hall  process  extracts  a  fraction  over  50  per 
cent,  of  metal  from  it.  The  alumina  to  furnish  one  pound  of 
aluminium  therefore  cost  in  1890  about  16  cents.  Since  then, 
the  alumina  is  calcined  in  Germany  before  shipment,  saving  in 
freight  and  customs  dues,  and  can  probably  be  laid  down  now 
in  New  York  at  S  cents  per  pound,  making  a  cost  of  10  cents 
per  pound  of  aluminium.     There  is,  besides  this,  a  small  waste 



of  bath  material,  which  costs  in  the  neighborhood  of  7  cents  per 
pound  to  make,  but  since  this  does  not  in  actual  running 
amount  to  over  2  pounds  per  100  pounds  of  aluminium  pro- 
duced, this  item  of  expense  is  quite  small. 

The  output  of  these  small  pots  was  about  one  pound  of 
metal  an  hour  from  each,  and  they  were  kept  in  continued  ope- 
ration for  several  weeks  at  a  time.     If  pure  alumina  is  used, 

Fig.  39. 

,,  "^^-^ /W''. 

pure  aluminium  is  produced ;  that  made  from  Bergius'  alumina 
averaging  over  98  per  cent.  pure. 

When  a  bath  has  been  put  into  operation,  the  metal  first 
produced  is  contaminated  with  the  silicon  and  iron  present  in 
the  bath  material,  but  in  a  few  days  these  are  completely  elim- 
inated, and  the  bath  material  is  almost  chemically  pure  save  for 
the  impurities  introduced  in  the  alumina. 

If  calcined,  selected  raw  bauxite  is  used  in  the  pots,  the 
metal  produced  averages  94  to  96  per  cent,  pure,  and  is  sold  for 


use  in  iron   and  steel.      Two  analyses  of  such  second  quality- 
metal  gave : 

Aluminium 94.16  9S'93 

Silicon 4.36  2.01 

Iron 1.48  2.06 

As  the  material  used  only  costs  about  i  cent  per  pound 
ready  to  put  into  the  pots,  and  about  2^  pounds  make  one  of 
metal,  this  second  quality  metal  costs  about  7  cents  less  per 
pound  than  the  first  quality. 

An  estimate  of  the  cost  of  producing  aluminium  in  this  plant 
in  1889,  at  the  rate  of  fifty  pounds  per  day,  is  as  follows: 

100  lbs.  calcined  alumina  @  8  cts =.  $8.00 

Fluorides  for  bath  @  7  cts =      .50 

Carbons  =    i.oo 

50  horse-power  engine =  15.00 

2  engineers  @  $3.00  per  diem =    6.00 

6  workmen  @  ;j2.oo        "        =  12.00 

Superintendence,  office  expenses,  etc .=  10.00 

Interest  on  plant,  rent,  etc ^    7.50 

Cost  of  about  50  lbs.  of  aluminium $60.00 

In  the  early  part  of  1890  the  plant  was  greatly  enlarged. 
The  additions  consisted  of  three  Babcock  and  Wilcox  boilers  of 
200  horse-power  each,  fired  by  natural  gas ;  two  200  Jiorse- 
power  Westinghouse  compound  engines ;  two  shunt-wound 
Westinghouse  dynamos  running  325  revolutions  per  minute, 
connected  in  parallel  and  giving  a  total  current  of  5000  amperes 
at  50  volts  tension.  The  conductors  for  this  current  were  two 
copper  bars,  6  inches  by  0.5  inch,  giving  a  total  cross-section 
of  6  square  inches.  This  gives  a  little  over  800  amperes  per 
square  inch  section.  This  current  operated  five  large  pots  con- 
nected in  series,  averaging  9  volts  to  a  pot.  These  large  pots 
are  of  one-quarter  inch  wrought  iron,  5  feet  long,  2%  feet  wide 
and  2  feet  deep,  with  a  carbon  lining  4  to  6  inches  thick,  and 
supported  on  bricks  to  keep  the  bottom  cool.  Above  are  two 
copper  bars  to  which  a  double  row  of  carbon  electrodes  are 
clamped,  there  being  10  on  each  row  or  20  in  all.     Each  of 


these  pots  produced  60  to  70  pounds  of  aluminium  a  day,  mak- 
ing the  production  of  the  entire  plant  in  1890  about  400 
pounds  per  day.  The  cost  of  aluminium,  working  on  this  scale, 
could  scarcely  have  been  over  $0.75  per  pound,  since  the 
metal  made  here  was  sold  during  1891  for  $1.00  per  pound. 

During  1891,  in  order  to  obtain  room  to  extend  and  cheapen 
fuel,  the  entire  plant  was  moved  to  New  Kensington,  Pa.,  on  the 
Allegheny  River  18  miles  from  Pittsburgh.  At  this  place  the 
capacity  of  the  plant  has  been  greatly  increased,  there  being  ap- 
proximately 1500  horse-power  employed,  and  the  output  having 
been  increased  to  lOOO  pounds  per  day  in  1893  and  to  nearly 
2000  pounds  per  day  in  1894.  Since  the  selling  price  has  been 
reduced  to  $0.50  per  pound,  it  is  evident  that  the  present 
cost  cannot  be  much  over  $0.40,  if  so  high.  Captain  A.  E. 
Hunt,  president  of  the  company,  is  authority  for  saying  that  as 
the  process  is  operated  on  an  increasing  scale,  and  more  exper- 
ience is  had  in  running  it,  the  cost  in  the  future  will  approxi- 
mate $0.20  per  pound,  the  lowest  limit  by  this  process. 

In  July,  1890,  a  plant  to  work  Hall's  process  was  put  into 
operation  at  Patricoft,  Lancashire,  England,  with  a  capacity  of 
about  300  pounds  of  aluminium  a  day.  This  plant  was  in 
operation  until  1894,  when  competition  from  Switzerland  com- 
pelled it  to  close. 

During  1894,  the  United  States  Company  have  been  con- 
structing a  larger  plant  at  Niagara  Falls,  being  furnished  power 
by  the  Niagara  Falls  Power  Co.  A  contract  has  been  made  to 
take  6000  horse-power,  and  the  plant,  so  far  constructed,  is  as 
follows :  * 

A  5000  horse-power  turbine,  in  the  Power  Company's  power- 
house, runs  a  5000  horse-power,  low  frequency,  alternating 
current  Tesla  dynamo.  This  machine,  at  full  speed,  gives  two 
currents  of  2500  volts  by  775  amperes  each,  alternating  50  times 
per  second.  The  exciting  circuit  is  continuous,  obtained  from 
the  main  circuit  by  a  rotary  transformer,  and  amounts  to  only 
0.2  per  cent,  of  the  main  current.     The  total  current  of  2500 

*This  plant  was  put  into  operation  on  August  26,  1895. 


volts  by  1550  amperes  is  conducted  through  an  underground 
tunnel  one-half  mile  to  the  aluminium  works,  through  copper 
rope  conductors,  with  a  total  section  of  4.3  square  inches,  with 
a  drop  in  potential  of  12  volts.  At  the  works,  the  current  is 
first  passed  through  a  set  of  stationary  transformers,  each  of 
250  horse-power,  in  which  the  current  is  reduced  from  2487 
volts  to  115  volts.  The  alternating  current  of  115  volts  next 
passes  to  rotary  transformers,  each  of  500  horse-power  and 
taking  the  current  from  two  stationary  transformers.  In  these 
the  alternating  current  of  115  volts  is  changed  to  a  direct  cur- 
rent of  160  volts,  the  quantity  of  current  furnished  by  each 
rotary  transformer  being  2500  amperes.  These  currents  of 
2500  amperes  by  160  volts  are  conducted  to  the  pot  room  on 
copper  bars  with  1.25  square  inch  section,  each  passing  through 
a  separate  switch-board,  on  which  are  shunt  ammeters  and  vol- 
meters,  and  then  passed  to  the  pots.  The  buildings  are  all  of 
iron,  the  main  reduction  room  being  180  by  85  feet. 

It  is  not  difScult  to  estimate  what  the  output  of  the  two  works 
will  be.  At  Pittsburgh  each  horse-power  of  electrical  energy 
produced  about  1.2  pounds  of  aluminium  per  day,  at  which  rate 
a  5000  horse-power  plant  should  make  6000  pounds,  equiva- 
lent in  round  numbers  to  1000  tons  a  year,  the  present  value  of 
which  is  $1,000,000. 

Reactions  and  efficiency  of  the  process. — Taking  the  first  small 
plant,  a  current  of  1800  amperes  in  two  vats  should  theoreti- 
cally produce  56.4  pounds  of  aluminium  per  day.  As  50 
pounds  were  obtained,  on  an  average,  the  efficiency  shown  in 
this  direction  is  nearly  90  percent.  As  only  about  2.5  volts 
out  of  the  9  volts  absorbed  by  the  bath,  is  used  in  decomposing 
the  alumina,  wc  have  about  30  per  cent,  of  the  current  thus 
utilized.  The  efficiency  over  all  is  therefore  90  per  cent,  of  30 
per  cent.=27  per  cent.  This  means  that  the  work  of  separat- 
ing aluminium  from  oxygen  represents  27  per  cent,  of  the  actual 
energy  of  the  current.  The  difference  between  9  and  2.5,  or 
6.5  volts,  is  absorbed  in  the  conduction  resistance  of  the  bath, 
being  converted   into   heat.     This  would  give  a  heat  develop- 


ment  of  6.25  X  1800x0.00024=  2.7  calories  per  second,  or 
9720  calories  per  hour.  To  this  we  may  add  the  heat  of 
oxidation  of  the  carbon  to  carbonic  oxide,  and  we  have  the 
total  heat  generated  in  the  bath.  A  balance  would  show  as 
follows : 

Heat  Developed  per  Hour. 

By  electrical  resistances 9720  calories. 

Oxidation  of  the  carbon 960        " 

Total 10680        " 

Heat  Distribution  per  Hour. 

Heating  2  pounds  alumina  to  900°  C 250  calories. 

Withdrawn  with  the  aluminium 17S        " 

Lost  by  radiation  and  conduction 10265        " 

Total 10680 

As  to  the  real  reaction  in  the  bath,  by  which  aluminium  is 
liberated,  several  metallurgists  have  taken  the  ground  that  the 
aluminium  fluoride  present  is  the  substance  primarily  disso- 
ciated by  the  current,  and  that  the  fluorine  set  free  at  the  anode 
immediately  acts  on  the  alumina  present  in  solution  and  re- 
forms aluminium  fluoride,  liberating  oxygen,  which  then  unites 
with  the  carbon.     According  to  this  view  the  reactions  are 

2AIF3  +  Current  =  2AI  +  6F. 
MO3  +  6F  =  2AIF,  +  3O. 

3C      +  3O  =  3CO. 

This  theory  must  assume  either  one  of  two  things ;  first, 
that  the  alumina  added  never  becomes  an  integral  part  of  the 
bath,  but  remains  suspended  mechanically;  or,  second,  that  if 
the  alumina  really  is  part  of  the  bath,  it  is  a  stronger  com- 
pound than  aluminium  fluoride,  and  therefore,  the  current 
decomposes  the  latter.  This  theory,  however,  involves  several 
contradictions.  If,  for  instance,  alumina  is  really  a  stronger 
compound  than  aluminium  fluoride,  how  could   the   gaseous 


fluorine  decompose  alumina,  forming  aluminium  fluoride? 
Since  gaseous  fluorine  can  decompose  alumina,  as  was  proven 
by  Moissan,  it  follows  that  alumina  is  therefore  a  weaker  com- 
pound than  aluminium  fluoride,  and  that  when  an  electric  cur- 
rent is  passed  through  a  bath  containing  these  two  compounds 
the  alumina  is  necessarily  the  first  to  be  decomposed.  The 
only  refuge  left  for  this  theory  is,  then,  to  maintain  that  the 
alumina  is  not  truly  dissolved  in  the  bath,  but  is  only  me- 
chanically suspended.  This,  however,  is  contrary  to  the  way 
in  which  the  bath  behaves.  Absorption  of  the  fluorine  could 
not  possibly  be  as  perfect  in  that  case  as  it  really  is  in  practice. 
Besides,  an  experiment  of  Mr.  Hall's  settles  the  case,  it  seems 
to  me,  beyond  question.  On  passing  the  current  through  an 
anode  of  clean  copper,  it  becomes  immediately  coated  with  a 
layer  of  copper  oxide.  If  fluorine  were  at  all  set  free,  it  would 
be  liberated  in  immediate  contact  with  the  anode,  and  copper 
fluoride  must  necessarily  have  been  formed ;  but  no  trace  of 
that  salt  is  observed.  It  thus  appears  impossible  to  me  that 
the  electric  current  does  anything  but  dissociate  oxygen  from 

It  has  been  suggested  that  the  alumina  is  dissolved  in  the 
bath  by  forming  aluminium  oxy-fluoride,  and  that  this  is  the 
substance  electrolyzed.  This  may  or  may  not  be  true,  but  there 
is  up  to  the  present  time  no  positive  proof  for  the  theory,  and 
several  circumstances  against  it.  No  chemist  has  as  yet  iso- 
lated and  analyzed  any  such  salt.  If  such  salt  is  formed,  the 
larger  the  proportion  of  aluminium  fluoride  in  the  bath,  the 
more  alumina  it  ought  to  dissolve.  But  cryolite  contains  40 
per  cent,  of  aluminium  fluoride,  and  dissolves  at  least  25  per 
cent,  of  its  weight  of  alumina  to  a  clear  solution,  while  the  salt 
AlFg.NaF,  containing  66  per  cent,  of  aluminium  fluoride,  and 
made  by  adding  aluminum  fluoride  to  cryolite,  dissolves  barely 
10  per  cent.  Further,  no  evolution  of  heat